Since 1975, NLM has included author-written abstracts from journals whose publishers gave the NLM permission for their use. These abstracts appear in the Abstract (AB) field. Over 50% of the documents in Ovid MEDLINE (R) contain abstracts. The abstract index contains all searchable words from the abstract.

All Fields (AF) is an alias for all of the fields which occur in the source documents, including value-added fields such as Abstract (AB)

The Authors (AU) field contains the authors of the article. The format for authors is last name followed by one or more initials: Smith JC or Smith J. Enter the last name, or if it is a common name, enter the last name and first initial. If you are unsure of the spelling of the last name (macdonald or mcdonald), enter one version and then scroll through the list of names to find the other.

Misspelled and corrected names are also included in the Authors Index to ensure all possible matches. Only correct author names display, while incorrectly spelled names are indexed along with the correct spelling of the name.

The Cited Reference DOI (CD) field contains the DOI information of the source citation.

This field displays in the Cited References (RF) field.

The Cited Reference Volume (CE) field contains the particular volume of the Cited Reference Source (CS).

It displays in the Cited References (RF) field.

The Cited Reference Page (CG) field contains the page information of the source citation.

It displays in the Cited References (RF) field.

The Conflict of Interest (CI) field contains disclosure statements as provided by the publisher. This field was introduced in 2017.

The Cited Reference Date (CQ) field contains at least the publication year for the respective reference. This field may contain month, day and/or time of publication or release.

This field displays in the Cited References (RF) field.

The Cited Reference Source (CS) field contains the full or abbreviated journal name of the source citation.

The Cited Reference Source displays in the Cited References (RF) field.

The Cited Reference PMCID (CZ) field contains the PMC identification number of the source citation reference.

It displays in the Cited References (RF) field.

The MeSH Date (DA) field contains the date MeSH terms were added to the citation. The MeSH date is the same as the Entrez date until MeSH are added. This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The Create Date (DC) field contains the date when it was added to PubMed. It was implemented with all PubMed records when the 2009 system became available on December 15, 2008. All records added to PubMed prior to implementation received a Create Date equal to Entrez Date (EZ). This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The MeSH Subject Headings (DE) field contains the Medical Subject Headings used by indexers at the National Library of Medicine (NLM) to describe the content of an article.

MeSH headings are entered into the index as phrases and should be searched as they appear in the NLM MeSH books.

The Publisher Item Identifier (DI) field uniquely identifies individual published documents that are provided by the publisher for new citation submitted.  The full PII appears as such e.g. S0036-36342008000600005

Search all PII's by replacing punctuation with spaces such as "S0036 36342008000600005".di. for the displayed PII of S0036-36342008000600005.

The DOI (DO) field contains the Digital Object Identifier - a unique and persistent digital identification code for any object of intellectual property. The DOI  itself consists of two parts: a prefix which is assigned to each publisher by the administrative DOI agency, e.g., "10.1097", and a suffix which is assigned by the publisher and can be any code that the publisher chooses, e.g., "00045415-200111000-00002".

The full DOI appears as such: "10.1097/00045415-200111000-00002". Search all DOI's replacing punctuation with spaces such as "10 1016 j adnc 2003 08 001".do. for the displayed DOI of 10.1016/j.adnc.2003.08.001. (all DOI information provided to Ovid is loaded as it becomes available from NLM).

The Date of Publication (DP) field consists of the date of publication for a citation, in the format Year Month(s) Day (1950 Dec 3). The Month and Day are not always present. This field is also displayed as part of the Source (SO) field.

The Subject Heading Word (DW) index allows you to retrieve every MeSH subject heading and Publication Type that include a particular word. Do this by searching a single word in the Subject Heading Word (DW) field.

The Equal Contributor (EC) field contains the journal publisher names who submit citation data to Pubmed.

The Entry Date (ED) field contains the NLM internal Date Completed (DCOM) which is the date processing of the record ends; i.e., MeSH Headings have been added, quality assurance validations are completed, and the completed record subsequently is distributed to PubMed. This is contrasted with the PubMed/MEDLINE Date Created, which is the date processing begins.

The Electronic Date of Publication (EP) is the date the record was sent to NLM for inclusion in MEDLINE (R). This index appears in the format YYYYMMDD.

The ISSN Electronic (ES) field contains the Electronic International Standard Serial Number (EISSN) for the journal in which an article was published. It appears as an 8 digit number, separated by a hyphen: 0028-4793. To retrieve all of the articles for a journal, search by the Journal Name (JN).

Both Electronic and Print ISSNs can be searched in the ISSN Print (IS) field.

The Entrez Date (EZ) is the date the citation was added to PubMed. However, prior to October 9, 2008, the Entrez Date was set equal to the Publication Date (DP) on records with publication dates before September 1997. Beginning on October 9, 2008, the Entrez Date is set equal to the Publication Date (DP) when the record enters PubMed more than twelve months after the date of publication. This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The Authors Full Name (FA) field contains the full name of the authors of the article when available.

Subheadings are qualifiers added to MeSH subject headings to refine their meaning.  Terms such as "etiology" or "therapy", when combined with a MeSH heading, give a precise idea of what an article covers.

The Floating Subheadings (FS) field contains both the 2-letter codes, such as "po" and the full headings, such as "poisoning". These are displayed following the corresponding MeSH Subject Headings.

Sometimes you may wish to retrieve every Floating Sub-heading that includes a particular word; this is done by searching the single word in the Floating Sub-heading Word (FX) field.

The Grant Country (GC) field contains the country of the organization that awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Grant Information (GI) field displays information about awarded grants, may contain Grant Number (NO), Grant Acronym (GR), Grant Organization (GO) and Grant Country (GC).

The Grant Organization (GO) field contains the full name of the organization that has awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Grant Acronym (GR) field contains the acronym of the organization that has awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Gene Symbol (GS) field contains Gene Symbols as they are entered into Ovid MEDLINE (R) in the original document. They often, but not always, conform to standardized human gene nomenclature. Ignore super or sub-scripts in entry of a gene symbol: psub 1450 would be entered p1450. Enter hyphens as in the original symbol.

The Gene Symbol field was added to Ovid MEDLINE (R) in 1991. Beginning in 1996, data will no longer be added to this field.

The Subject Heading Word (HW) index allows you to retrieve every Ovid Descriptor that includes a particular word. Do this by searching a single word in the Subject Heading Word (HW) field.

The Investigator Affiliation (IA) field contains author's full name and its affiliation to the investigator of the article.

The Article Identifier (ID) field may contain an identifier that links with records in the publisher's system. The Article Identifier values may include the controlled publisher dentifier (PII) or the digital object identifier (DOI). It is most often used for LinkOut, and is not considered part of the citation source information.

The Indexing Method (IG) field was introduced by the NLM in September 2018. It will only be present in records if a value is specified. If Indexing Method is not present in status MEDLINE records, the indexing method is fully human indexed.

Values for Indexing Method (IG) are:
Curated - MeSH indexing is provided algorithmically and a human reviewed (and possibly modified) the algorithm results
Automated - MeSH indexing is provided algorithmically

The ISSN Linking (IL) index contains an identifier intended to provide a mechanism to group the various medium versions of a continuing resource. The purpose of the ISSN-L is to provide a mechanism for grouping, or collocating, the various medium versions of a resource, for instance, the print and online versions of a journal per ISO 3297 standards. "The first ISSN assigned, in the ISSN Register, to any medium version of a continuing resource shall be designated by default to function also as the ISSN-L and shall apply to all other media versions of that resource identified in the ISSN Register.

The ISSN Linking field will be used only for new records added during the 2008 production year (although NLM still does not know the timing when all will be in place to start to appear on records).

The Institution (IN) field contains all author full names and its affiliations, which is usually the source for a reprint of the article. This information can be searched in most documents since 1988, but records from earlier years which were added to the database after 1988 may also contain institution information. Beginning with documents indexed in 1996, all author's email address will also be included, if present in the journal.

The information is taken from the source document and is not standardized. Enter the single most descriptive word in an institution (harvard, not university). Consider both full spellings and abbreviations.

The ISO Journal Abbreviation (IO) field contains journal abbreviations. Those created prior to 2007 did not necessarily conform to the ISO standard. ISO Journal Abbreviations created after this date are identical to the Journal Abbreviation (JA) field. In November 2009 ISO abbreviations were retrospectively assigned for every record from a journal that was currently indexed for MEDLINE at that time.

The Investigator (IR) field contains personal names of individuals (e.g., collaborators and investigators) who are not authors of a paper but rather are listed in the paper as members of a collective/corporate group that is an author of the paper.

The format for authors is last name followed by one or more initials:  Smith JC or Smith J.

The ISSN Print (IS) field contains the International Standard Serial Number (ISSN) for the journal in which an article was published. It appears as an 8 digit number, separated by a hyphen: 0028-4793. To retrieve all of the articles for a journal, search by the Journal Name (JN). Both Electronic and Print ISSNs can be searched in the IS index.

The Investigator NameID (IX) field is defined to contain a unique identifier associated with the name. The values in the Identifier attribute Source will designate the organizational authority that established the unique identifier.

The Journal Abbreviation (JA) field contains the abbreviation of the journal in which the article was published.

The NLM Journal Code (JC) is an alpha-numeric code established by NLM which uniquely identifies every journal indexed in the NLM databases. Only the 7 digit code is searchable, in some cases the 3 digit alpha-numeric code will display as well.

The Journal Name (JN) field contains the full name of the journal in which the article was published. Journal names are indexed as phrases, so enter enough letters of the journal name to locate the name in the index:  new engl (for New England Journal of Medicine). This field usually displays as part of the Source (SO) field.

If the first word of a Journal Name is "The", it has been stripped off.

The Journal Word (JW) index contains individual words from every journal name in Ovid MEDLINE (R). This field displays as part of the Source (SO) field.

The Keyword Heading Word (KF) index allows you to retrieve every Keyword Heading assigned by authors that include a particular word. Do this by searching a single word in the Keyword Heading Word (KF) field.

The Keyword Heading (KW) field contains the Keyword Headings assigned by authors. Keyword Headings are the author keywords. To retrieve every Keyword Heading that includes a particular word, search for the word in the Keyword Heading Word (KF) field.

The Language (LG) field contains the language(s) of publication of an article. The language name will appear in the index as the full form and a 3-letter code (such as fre for French) and as the full name French. The codes are usually, but not always, the first three letters of the language name.

The Locally Held (LH) field indicates (with a "Y" or an "N") if a journal is held locally.

The Local Messages (LM) field contains messages created by the System Administrator to indicate information about journals held in your local library system.

The NLM Journal Name (NJ) field contains the full name of the journal in which an article was published.

The Name of Substance (NM) index contains single words from the CAS Registry/EC Number/Name (RN) field and is used to search portions of chemical names. This field displays as part of the CAS Registry/EC Number/Name (RN) field.

The Name of Substance (NM) field was added to Ovid MEDLINE (R) in 1980.

This field displays as part of the Grant Information (GI) field.

The Number of References (NR) field contains the number of bibliographic references listed in the review article.

Effective October 1, 2010 NLM discontinued the practice of including the number of bibliographic references listed in articles cited in MEDLINE. NLM had included the number of references for the following Publication Types: Review; Consensus Development Conference; Consensus Development Conference, NIH; Interactive Tutorial; Meta-Analysis. This change in policy is prospective only; we will not remove number of references data from existing citations.

This field displays in the Abstract (AB) and Title (TI) when available.

The General Note (NT) field contains general supplementary information about an item. The notes may include information on the availability of a bibliography, ordering information for dissertations or hearings, or general summaries of materials such as manuals or scripts. A series title may appear for a book or for audiovisual materials.

The Other Abstract (OA) field can include the Collaborating Partner, a brief abstract, Copyright and Language of the Other Abstract. The OA field is indexed in the Abstract (AB) field, and contains all searchable words from the Other Abstract.

Collaborating Partners include:

The Outline Headings (OH) field searches the author-defined section names of full text documents. You can use this field to locate documents containing discussions of significant length regarding a desired topic. The section names are listed under the "Outline" header on the full text display window.

The Other ID (OI) is a unique alpha-numeric code. In particular, it will contain the PubMed Central Identifier (PMCID), where the alphabetical prefix 'PMC' precedes the identifier. If the publisher has embargoed access to the full text, the date of availability in PubMed Central will be noted. When the embargo is lifted, a revised record with the date of availability removed will be released.

Other ID's are entered into the index as phrases. In particular, PMC ID's should be searched as how the alpha-numeric code appears in PubMed Central (PMC).

The Organism Supplementary Concept (OS) field contains the Protocol Class 4 SCR terms that includes viruses and other organisms. The Organism Supplementary Concept (OS) terms are phrase indexed.

They appear for the first time in the 2018 MeSH and were made available as a means to index emerging viruses and other pathogenic organisms as they occur in the literature without delay.

The Primary Author (PA) field contains the first author listed for the article.  This allows users to search for articles by any primary author. Author names display in Authors (AU) and Authors Full Name (FA) fields. Searching for smith rh.pa. will return results where Smith RH was listed as the main author of the article.

The Page (PG) field consists of the inclusive pagination of a journal article. Often a journal title combined with the beginning page number is enough to locate a citation. You can search for pages with alphanumeric characters, such as "a1.pg." This field displays as part of the Source (SO) field.

The Publication History Status (PH) field contains information from the publisher regarding important events in the publishing process. It contains a date, and one of the following values for each date in the publication history:

The Publication History Status (PH) field is word-indexed.

The PMC Identifier (PM) is a unique alpha-numeric code. In particular, it will contain the PubMed Central Identifier (PMCID), where the alphabetical prefix 'PMC' precedes the identifier. If the publisher has embargoed access to the full text, the date of availability in PubMed Central will be noted. When the embargo is lifted, a revised record with the date of availability removed will be released.

Other ID's are entered into the index as phrases. In particular, PMC ID's should be searched as how the alpha-numeric code appears in PubMed Central (PMC).

The Personal Name As Subject (PN) field displays the name of a well-known person if they are discussed in an article, such as an interview or obituary.

The format for Personal Name is the same as for Author -- last name and initials: Bach JS. Enter a last name and one initial if known.

The Publication Status (PP) field contains the current status of the publication, as submitted by the publisher. Possible values are:

The Pubmed Central Release (PQ) field contains the embargo date associated with the availability of the published article in PMC.

The Protocol Supplementary Concept (PS) field contains the Protocol Class 2 SCR terms. These terms were previously exported in CAS Registry/EC Number/Name of Substance (RN) in MEDLINE/PubMed. The PS terms are phrase indexed.

With the 2011 reload, Protocol Supplementary Concept (PS) will be loaded separately only for new records added during 2011 production year.

In addition to indexing documents with Medical Subject Headings, the indexers at the National Library of Medicine assign terms to describe the article type. Publication Types include such classifications as reviews, clinical trials, directories and letters. These terms appear in the Publication Type (PT) field.

To view the index, enter enough letters to distinguish a publication type (jour for "journal article"); the entire index is quickly scrollable to determine all possible publication types.

With the 2005 reload, Publication Types are also loaded into the MeSH. Because some Publication Types are also MeSH terms, the syntax to enter the Tree is "Randomized controlled trial [publication type]". To post the results from the Tree without entering the Tree, the syntax is: "Randomized controlled trial [publication type]"/ or Randomized controlled trial.pt.

The Protocol Supplementary Concept Word (PX) index allows the users to retrieve single terms from the Protocol Supplementary Concept (PS) field.

The Cited References (RF) field contains a complete or partial reference list to the source citation.

Use RF to simultaneously search in all searchable parts of the Cited References field, including Cited Reference Date (CQ), Cited Reference Authors, Cited Reference Source (CS), Cited Reference Title, Cited Reference DOI (CD), Cited Reference Volume (CE), Cited Reference Page (CG), Cited Reference Issue (RP), Cited Reference PMCID (CZ), Cited Reference Publisher Identifier (RY) and Cited Reference UI (RZ).

The Reference Title Index (RL) allows the users to search for the reference(s) title which may contain one or multiple source citations.

It displays in the Cited References (RF) field.

The RN field can contain the following:
- The unique 10-digit Unique Ingredient Identifiers (UNIIs) assigned by the Food and Drug Administration (FDA) Substance Registration System (SRS)
- The 5- to 9-digit Chemical Abstracts Service (CAS) for Registry Numbers
- The number EC derived from Enzyme Nomenclature to designate a particular enzyme

Examples:

To find UNII number 8R78F6L9VO (Sumatriptan) search for: 8R78F6L9VO Sumatriptan.rn. or: 8R78F6L9VO*.rn.
To find CAS number 54-16-0 (Hydroxyindoleacetic Acid)), search for: 54-16-0 Hydroxyindoleacetic Acid.rn.
To find EC number (EC 1-14-14-1 (Aryl Hydrocarbon Hydroxylases)), search for: ec-1-14-14-1 aryl hydrocarbon hydroxylases.rn.

A zero (0) is a valid value when an actual number cannot be located or is not yet available.

Note: NLM has not added Chemical Abstracts Service (CAS) registry numbers to MeSH since 1998, therefore only registry numbers that were previously available are displayed in the MEDLINE record. At this time, UNIIs are used only in Registry Number of Supplementary Concept Records.

The Record Owner (RO) field contains the owner of the record.

The Cited Reference Issue (RP) field contains the issue information of the journal in which the citation appears.

It displays in the Cited References (RF) field.

The Rare Disease Supplementary Concept (RS) field contains the Protocol Class 3 SCR terms. The RS terms are phrase indexed.

Beginning with 2011 MEDLINE/PubMed data, Rare Disease Class 3 SCRs are also going to be exported.

The Rare Disease Supplementary Concept Word (RX) index allows the users to retrieve single terms from the Rare Disease Supplementary Concept (RS) field.

The Cited Reference Publisher Identifier (RY) field contains the Publisher Item Identifier (DI) of the source citation.

It displays in the Cited References (RF) field.

The Cited Reference UI (RZ) field contains the PMID of the source citation.

It displays in the Cited References (RF) field as part of the link URL to NLM.

The Secondary Source AN (SA) index contains the unique identifiers of outside resources discussed in MEDLINE articles. The display will include the Secondary Source ID (SI) and the unique identifier seperated by a forward slash (RefSeq/NM_020533). If you wish to search all works from a particular databank use the Secondary Source ID (SI) index: refseq.si.

The Journal Subset (SB) field identifies the subset for MEDLINE records from certain journal lists on specialized topics. The NLM discontinued the Journal Subset (SB) indexing for MEDLINE/PubMed with the 2022 reload, with the exception of "index medicus.sb." and "oldmedline citations.sb.". Ovid replaced the corresponding Journal subset limits new journal selections based on NLM Catalog searches, using matching MeSH terms and title words to create new lists of titles for the below journal subsets. We strongly recommend that you review your search strategies if you used the Journal Subset (SB) field, or limits in search strategies prior to the 2022 reload.

Do not confuse these journal subsets with the Topics subsets available on PubMed's Limits screen, which are based on different search strategies.

The Season (SE) field contains the month or season that the citation article was published.
The field usually consists of a three-character alphabetic abbreviation of the month or season.

Example: Win

The Ovid Descriptor (SH) field contains the Ovid Descriptor that is assigned to the record to describe the content and is based on the Nursing Subject Thesaurus. These are largely based on NLM's MeSH and other sources such as Library of Congress.

The Secondary Source ID (SI) identifies secondary source databanks with unique identifiers of outside resources discussed in MEDLINE articles. The field is composed of the source acronym:  GENBANK

The Secondary Source ID (SI) formerly known as the Molecular Sequence (MS) field was added to Ovid MEDLINE (R) in 1988.

The Secondary Source Link (SL) index contains the URL to the outside resources discussed in MEDLINE articles when the Secondary Source ID is either ClinicalTrials.gov or ISRCTN. The index contains the URL, for searching ease use the Secondary Source AN (SA) index: nct00000150.sa.

The Source (SO) field includes a display of all the basic information needed to locate a record, including the full Journal Name (JN), Issue/Part (IP), Page (PG), Volume (VO) and Date of Publication (DP).

The Status (ST) field contains the status of the citation.

In-Data-Review records have passed the first step in quality control and will either be reissued as In-process records or go directly to PubMed-not-MEDLINE as the final record status.

In-Process records are electronically submitted and have gone through the second citation-level review.

Medline records have passed all steps in quality control and have been indexed.

PubMed-not-MEDLINE records have gone through the second citation-level review, but are from non-Medline journals or precede the date a journal was selected for MEDLINE indexing but are now being submitted for inclusion.

The Title Comment (TC) field pertains to and contains citations to associated journal publications, e.g., comments, errata, retractions, or cited references. These data enable links between the record at hand and its associated citations.

This field begins with the indication of comment or correction type (see Comments (CM) fields for a full list of types) and then displays the Journal Abbreviation (JA), Date of Publication (DP), Volume (VO), Issue/Part (IP) and Page (PG).

The Title (TI) field contains the English language version of a title. For documents which were not written in English, the original or transliterated title appears in a separate field, Original Title (OT).

The title sometimes includes notes, in brackets, about the article, such as an indication that it is a letter, editorial, or comment.

The Text Word (TW) field is an alias for all of the fields in a database which contain text words and which are appropriate for a subject search.

The Text Word field in OVRN includes Title (TI) and Abstract (AB).

The Unique Identifier (UI) field contains the PMID (PubMed identifier or PubMed unique identifier) that is the unique number assigned to each PubMed record.

PMIDs do not change over time or during processing and are never reused.

The Update Date (UP) field contains the date the record was added to Ovid Nursing (R) since reload completion.  The Update Date for existing records changes with each global reload to reflect the date Ovid starts processing the reload data. The UP field appears in the format YYYYMMDD.

Version Date (VD) field is a new model of publishing referred to as "versioning" whereby multiple versions of the same online article are released, sometimes in quick succession and sometimes almost as soon as the original article has been published. Although the Version Date value may be different from the Date of Publication, it might be the same as Date of Publication if the new version was released later the same day. Version Date is phrase indexed.

NLM does not expect many journals will publish versions, thus the incidence of versioned citations will be small. PLos Currents Influenza, a PubMed Central journal, is one example (and is the only journal involved at this time).

The Catalog Holdings (XH) field indicates (with a "Y" or an "N") if a journal is held locally.

Ovid Nursing Databse is comprised of data from the National Library of Medicine's (NLM) MEDLINE and other Ovid database journals of which the copyrights for the journal articles are held by their respective publishers. NLM represents that the data provided is formulated with a reasonable standard of care. Except for this representation, and as otherwise specifically provided herein, NLM makes no representations or warranties, expressed or implied. This includes but is not limited to, any implied warranty of merchantability or fitness for a particular purpose, with respect to the NLM databases, and NLM specifically disclaims any such warranties and representations. Downloading data is permitted for personal use only. Some material in the NLM databases is from copyrighted publications of the respective copyright claimants. Users of the NLM databases are solely responsible for compliance with any copyright restrictions and are referred to the publication data appearing in the bibliographic citations, as well as to the copyright notices appearing in the original publications, all of which are hereby incorporated by reference.

The following use of data from article with a Record Owner of NLM requires no written permission from or signed license agreement with NLM.

Users may download small amounts of data, e.g., the bibliographic citation and MeSH® terms, for a small number of NLM citations for redistribution either via a printed publication or in electronic form using the Internet, World Wide Web, etc. Downloading from a MEDLARS licensee, such as OVID is subject to the licensee's approval.

Definitions:

1. Download includes ftping results of an online search, arranging for the results of an automatic stored search to be available for ftp, ftping MEDLARS data from the NLM server (nlmpubs.nlm.nih.gov), or a traditional download using a modem.
2. Small is defined as approximately 1,000 records per month from MEDLINE; 12,000 per year. Retrospective pulls of MEDLINE may include up to approximately 12,000 records for each year covered. For other MEDLARS databases, fewer than 25% of records in the file may be downloaded. For larger portions of a MEDLARS database, contact [email protected] or 301-496-7706 for licensing information.
3. Data is defined as bibliographic citations and MeSH terms. This document grants permission to download only the bibliographic citations and MeSH terms, it does not cover author abstracts from the journals which are included in MEDLINE and other MEDLARS databases. Users should obtain an opinion from their legal counsel for any use they plan for the author-generated abstracts in the MEDLARS database.

Terms and Conditions:

Users must ensure that all downloaded publicly accessible data stored in electronic form for over one year must be in compliance with the following provisions of the NLM license agreement:

1. Users of this data must be provided a clear description of how the product/service was derived, indicating the currency and the source database.
2. At least annually, the data downloaded must be corrected to incorporate the corrections NLM has made to these records during the year and in year end maintenance. MEDLARS data in any subsequently produced product/service must be carefully checked with that maintained on NLM's version of the database at the end of each calendar year and corrections made.
3. Users are advised to consult legal counsel to ensure compliance with intellectual property laws. NLM cannot provide advice about copyright issues.
4. Since NLM goes to considerable efforts to assign MeSH terms, it prefers that these be retained as assigned by the indexers.
5. All downloaded NLM records (or portions thereof) must be labeled so as to identify NLM as the source.
6. Trademark symbols must properly be used when referring to the NLM databases, system and products. A product/service using downloaded data must be named in a fashion that clearly distinguishes it from NLM-produced databases accessible at NLM.

The following general usage statement applies to all journal articles other than NLM articles:

Articles in any pre-publication stage can change significantly before final publication. Because Ovid’s PAP articles present data that is in-process toward final publication, their statements, opinions, and information may contain errors in facts, figures, or interpretation. With this in mind, apply responsibly any information gained from Journals@Ovid PAP articles. Accordingly, the publisher, editors, authors of PAP articles, and their respective employees accept no liability for consequences of any inaccurate or misleading data, opinion, or statement.