NLM creates links in PubMed between citations for original articles and citations for retraction and erratum notices, expressions of concern, corrected and republished articles, comments, duplicate publications, updates, patient summaries, and republished articles. These links help users find the various citations associated with a given article. For help searching PubMed for linking citations, please see Comment Correction Type in online help.
NLM encourages publishers to follow the retraction, errata, and similar guidelines established by the International Committee of Medical Journal Editors and the Committee on Publication Ethics.
Errata
NLM does not differentiate between errors that originate in the publication process and those that result from errors of scientific logic or methodology, because journal editors do not make this distinction consistently or clearly. Corrections, corrigenda, addenda, and partial retractions (such as for a single graph, statement, table or image) for previously published articles are all uniformly considered by NLM to be errata.
Errata may be published to correct or add text or information that appears anywhere within an earlier published article. Errata must be labeled and published in citable form; that is, the erratum must appear on a numbered page in an issue of the journal that published the original article. For online journals or online-only content, the erratum must be readily discernable in the table of contents of a subsequent issue and must be associated with identifiable pagination or elocation. Publishers submit to NLM the citation data for an erratum notice and can find guidance on data submission at XML help for data providers: Errata, retractions and comments.
NLM links the citation for the erratum notice to the citation for the referent article, and the citation for the erratum notice is automatically indexed with the Publication Type Published Erratum [PT]. The citation for the erratum notice contains the phrase “Erratum for: [article title],” and the citation for the referent article contains the phrase “Erratum in: [article title].”
If the erratum involves correction of text or information that is part of the corresponding PubMed citation, such as the author, title or abstract, the publisher is responsible for updating the article citation to reflect the correction. Publishers can edit citation data at any time with the PubMed Data Management System (PMDM). More information may be found in PMDM help.
When appropriate, NLM will retain the ability to retrieve the data via the previous, uncorrected form of the citation. For example, if an author name has been corrected, NLM will retain the ability to search and retrieve the citation via the originally published, incorrect form of the author name, in addition to the ability to search and retrieve the citation via the corrected form of the author name. A notice about the correction in the citation will show both the incorrect spelling of the name and the corrected form.
If the erratum involves correction of a portion of the article that is not included in the NLM citation, such as the text, graphs, or tables, the erratum notice is simply linked to the citation for the corrected article.
For more information on errata in PubMed, please see PubMed help.
Example:
Erratum in: PMID 28321512
Erratum for: PMID 28405767
Retractions and Retraction Notices
Journals may retract or withdraw articles based on information from their authors, academic or institutional sponsor, editor or publisher, because of pervasive error or unsubstantiated or irreproducible data. NLM creates links in PubMed between citations for original articles and citations for retraction notices based on information published by the journal. NLM does not differentiate between articles that are retracted because of honest error and those that are retracted because of scientific misconduct or plagiarism.
Retraction notices must clearly state that the article in question is being retracted or withdrawn in whole by an author of the retracted paper or author’s legal counsel; by the head of the department, dean, or director of the laboratory where the paper was produced; or by the journal editor.
Retraction notices must be labeled and published in citable form; that is, the retraction must appear on a numbered page in an issue of the journal that published the retracted article. For online journals or online-only content, the retraction notice must be readily discernible in the table of contents of a subsequent issue and must be associated with identifiable pagination or elocation.
Data providers can find more guidance in XML help for data providers: Errata, retractions and comments and XML help for data providers: Ahead of print Withdrawn Policy.
The Publication Type Retraction of Publication [PT] is assigned to the citation for the retraction notice, and the citation is linked to the citation for the retracted article. The Publication Type Retracted Publication [PT] is assigned to the retracted article. Citations for retraction notices contain the phrase “Retraction of: [article title],” and citations for retracted articles contain the phrase “Retraction in: [article title].”
Example:
Retraction in: PMID 19717156
Retraction of: PMID 27326436
Expression of Concern
An expression of concern about the integrity of a published article is typically written by an editor using that phrase in the item title. It is the responsibility of the editor to initiate appropriate investigative procedures, discover the outcome of the investigation, and notify readers of that outcome in a subsequent issue of the journal. The outcome may require the publication of a retraction notice. The citation for an expression of concern is linked to the citation for the referent article. Citations for expressions of concern contain the phrase “Expression of concern for: [article title],” and citations for the referent article contain the phrase “Expression of concern in: [article title].”
Example:
Expression of concern in: PMID 27552597
Expression of concern for: PMID 27939408
Comments
Comments are substantive articles, letters or editorials that challenge, refute, support, or expand upon another published item. Among the types of articles that are considered comments are: invited comments on another article; letters to the editor that were inspired by a previous article; and articles that provide additional information to previous articles. A mere mention of one or more articles in the text or references does not constitute a comment. The commenting article must have been written primarily for the purpose of making a comment—that is, of drawing the reader’s attention to the referent article.
Since 1989, NLM has created links between commenting articles and the articles to which they refer. Citations for comments include the phrase “Comment on: [article title],” and citations for the referent article include the phrase “Comment in: [article title].” A commenting citation is indexed with the Publication Type Comment [PT].
The majority of comment links are for substantive comments published within the same journal title. Links are also made for comments to articles previously published in different journals when they consist of a substantive summary and analytical evaluation, especially in relation to evidence-based medicine. Some journals are largely devoted to this type of comment, such as Evidence-Based Nursing and Evidence-Based Mental Health.
Example:
Comment on: PMID 28264092
Comment in: PMID 28264080
Author Responses to Comments
Frequently, a published letter that NLM considers a comment will be immediately followed by a response written by the author(s) of the original article. Citations for such published author responses are linked to the commenting letter as well as the original article.
Prior to 2013, author replies were not cited separately but had their pagination included in the pagination of the commenting letter.
From 2013 to 2015, if the author reply had a non-distinctive title such as “Reply” or “Author Reply,” the title was amended to include the PMID of the commenting letter in the format “Author Reply: To PMID 12345678.”
Effective in 2016, NLM stopped editing the article title of author replies and accepts the article title as submitted by the publisher.
Example:
Comment in: PMID 25732203
Comment on: PMID 26899895
Comment on: PMID 27062210
Corrected and Republished Articles
Occasionally, a journal may correct a previously published article by republishing the article in its entirety, often to rectify an editorial or printing error in the original article. The citation for the republished article is indexed with the additional Publication Type of Corrected and Republished Article [PT] and is linked to the citation for the original article. Citations for a republished article include the phrase “Corrected and republished from: [article title],” and citations for the original article include the phrase “Corrected and republished in: [article title].”
Example:
Corrected and republished in: PMID 25661664
Corrected and republished from: PMID 27049155
Journals also may correct a previously published article that was retracted due to errors in science. The citation for the republished article is indexed with the Publication Type of Corrected and Republished Article [PT] and is linked to the citation for the retracted article. Citations for a republished article include the phrase “Retracted and republished from: [article title],” and citations for the retracted article include the phrase “Retracted and republished in: [article title].”
Example:
Retracted and republished in: PMID 23432189
Retracted and republished from: PMID 29897866
Duplicate Publications
When NLM identifies an article that duplicates another article without acknowledgement, the citations for both articles are assigned the Publication Type of Duplicate Publication [PT]. Duplication may occur inadvertently through multiple submissions of a manuscript to different journals. When duplication is acknowledged and intentional to achieve wider dissemination of an article, such as a policy statement, the Duplicate Publication [PT] is not assigned.
The Publication Type of Duplicate Publication [PT] may be added to a citation with or without a formal notification from authors or journal editors. In the indexing process, indexers sometimes recognize duplicates; however, NLM does not routinely examine articles for originality.
Example:
A notice of duplicate publication is sometimes published within a journal when an occurrence of duplicate publication is discovered. Such notices are cited and indexed with the MeSH subject heading Duplicate Publication as Topic [MH], and comment linkages are created to each of the citations for the duplicate articles.
Updated Articles
An article that updates a previous article must explicitly state that it is an updated version of a previously published article or must appear in a journal that routinely publishes such updates as its primary content. NLM began to link citations for updated articles to the citation for the original article in 2001. The citation for the updated article contains the phrase “Update of: [article title],” and the citation for the original article contains the phrase “Update in: [article title].” Updated articles occur primarily in the Cochrane Database of Systematic Reviews.
Example:
Update in: PMID 15846749
Update of: PMID 18254074
Patient Summaries
Some journals routinely publish patient summaries of full articles that appear in the same journal issue. The summaries are intended for patients or the lay public to explain in non-technical terms the scientific or medical findings reported in the full article.
These citations are indexed with the Publication Type of Patient Education Handout [PT] and are linked to the corresponding citation for the full, scientific article. Citations for patient summaries contain the phrase “Original report in: [article title],” and citations for the original scientific article contain the phrase “Summary for patients in: [article title].”
Summary for patients in: PMID 26903390
Original report in: PMID 26902107
Republished (Reprinted) Articles
Journals occasionally republish (i.e., reprint) a significant article that was recently published in another journal. Such republished or reprinted articles are cited, and links are created between the citations for the original and republished article. The citation for the republished article is not indexed with MeSH headings. The citation for the republished article contains the phrase “Republished from: [article title],” and the citation for the original article contains the phrase “Republished in: [article title].”
This policy applies if there is an explicit indication that the article is being republished or reprinted, even if it is being republished in an abridged or different version from the original. (However, there is a distinction from corrected and republished articles, for which a different policy and pair of citation links are used.)
Example:
Republished in: PMID 18234913
Republished from: PMID 18364410
Last Reviewed: August 8, 2018