The Vancouver system, also known as Vancouver reference style or the author-number system, is a citation style. It is popular in the physical sciences, and is one of two referencing systems normally used in medicine, the other being the author-date, or "Harvard", system.
Hundreds of scientific journals use author-number systems, which have existed for over a century. They all follow the same essential logic, although the trivial details of the output mask, such as punctuation, casing of titles, and italic, vary widely among them. The names "Vancouver system" or "Vancouver style" have existed since 1978. They have two senses—a broad sense meaning any author-number system (regardless of the trivial output mask details), and a narrow sense referring to the specific author-number incarnation used by the ICMJE Recommendations (Uniform Requirements for Manuscripts). The latest version of the latter is Citing Medicine, per the References > Style and Format section of the ICMJE Recommendations. Citing Medicine style is the style used by MEDLINE and PubMed; thus, the output mask seen at PubMed is "Vancouver style" in its specific/narrow sense.
As an example of the two senses, AMA reference style is Vancouver style in the broad sense of the term (because it is an author-number system that conforms to the URMs), but not in the narrow sense (because it has trivial output mask differences from NLM/PubMed style). The latter is why the output styles (masks) of reference management software offer a distinction between Vancouver or AMA.
Author-number systems have existed for over a century and throughout that time have been one of the main types of citation style in scientific journals (the other being author-date). In 1978, a committee of editors from various medical journals, the International Committee of Medical Journal Editors (ICMJE), met in Vancouver, BC, Canada to agree to a unified set of requirements for the articles of such journals. This meeting led to the establishment of the Uniform Requirements for Manuscripts Submitted to Biomedical Journals (URMs). Part of the URMs is the reference style, for which the ICMJE selected the long-established author-number principle.
The URMs were developed 15 years before the World Wide Web debuted. During those years, they were published as articles or supplements in various ICMJE member journals. These included the 1991 BMJ publication, the 1995 CMAJ publication and the 1997 Annals of Internal Medicine publication. In the late 1990s and early 2000s, journals were asked to cite the 1997 JAMA version when reprinting the Uniform requirements.
In the early 2000s, with the Web having become a major force in academic life, the idea gradually took hold that the logical home for the latest edition of the URMs would be the ICMJE website itself (as opposed to whichever journal article or supplement had most recently published an update). For example, as of 2004, the editors of Haematologica decided simply to invite their authors to visit www.icmje.org for the 2003 revision of the Uniform requirements.
Since the early to mid-2000s, the United States National Library of Medicine (which runs MEDLINE and PubMed) has hosted the ICMJE's "Sample References" pages. Around 2007, the NLM created Citing Medicine, its style guide for citation style, as a new home for the style's details. The ICMJE Recommendations now point to Citing Medicine as the home for the formatting details of Vancouver style. For example, in the December 2013 edition of the ICMJE Recommendations, the relevant paragraph is IV.A.3.g.ii. (References > Style and Format).
Several descriptions of the Vancouver system says that the number can be placed outside the text punctuation to avoid disruption to the flow of the text, or be placed inside the text punctuation, and that there are different cultures in different traditions. The first method is recommended by some universities and colleges, while the latter method is required by scentific publications such as the MLA and IEEE except for in the end of a block quotaton. (IEEE are using Vancouver style labels within brackets, for example  to cite the first reference in the list, but otherwise refer to Chicago Style Manual.) The original Vancouver system documents (the ICMJE recommendations and Uniform Requirements for Manuscripts Submitted to Biomedical Journals) do not discuss placement of the citation mark.
Format of citations
Different formats exist for different types of sources, e.g. books, journal articles etc. Author names are abbreviated to at most two initials. Although Citing Medicine does not explicitly mandate merging initials (e.g. "R. K." would be merged into "RK"), the examples used throughout the book do.
Standard journal articles
- Leurs R, Church MK, Taglialatela M. H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects. Clin Exp Allergy. 2002 Apr;32(4):489-98.
- Tashiro J, Yamaguchi S, Ishii T, Suzuki A, Kondo H, Morita Y, Hara K, Koyama I. Inferior oncological prognosis of surgery without oral chemotherapy for stage III colon cancer in clinical settings. World J Surg Oncol. 2014 May 10;12(1):145. [Epub ahead of print]
As an option, if a journal carries continuous pagination throughout a volume (as many medical journals do), the month and issue number may be omitted.
- Thomas MC. Diuretics, ACE inhibitors and NSAIDs – the triple whammy. Med J Aust. 2000;172:184-5.
The NLM lists all authors for all articles, because it is appropriate for capturing all authors and all of their publications in the MEDLINE database to be found by searches. However, in the reference lists of articles, most journals truncate the list after 3 or 6 names, followed by "et al." (which most medical journals do not italicize):
- Guilbert TW, Morgan WJ, Zeiger RS, Mauger DT, Boehmer SJ, Szefler SJ, et al. Long-term inhaled corticosteroids in preschool children at high risk for asthma. N Engl J Med. 2006 May 11;354(19):1985-97.
- von Itzstein M, Wu WY, Kok GB, Pegg MS, Dyason JC, Jin B, et al. Rational design of potent sialidase-based inhibitors of influenza virus replication. Nature. 1993 Jun 3;363(6428):418-23. PMID 8502295.
NLM elides ending page numbers and uses a hyphen as the range indicating character (184-5). Many journals do likewise, whereas others expand the ending page numbers in full (184-185), use an en dash instead of a hyphen (184–5), or both (184–185).
Virtually all medical journal articles are published online. Many are published online only, and many others are published online ahead of print. For the date of online publication, at the end of the citation NLM puts "[Epub Year Mon Day]" (for online-only publication) or "[Epub ahead of print]" for online ahead of print (with the month and day following the year in its normal position). In contrast, AMA style puts "[published online Month Day, Year]" at the end of the article title. It no longer uses the term "Epub" and no longer includes the words "ahead of print". It omits the year from its normal location after the journal title abbreviation if there is no print data to give (online-only publication).
The titles of journals are abbreviated. There are no periods in the abbreviation. A period comes after the abbreviation, delimiting it from the next field. The abbreviations are standardized. The standardization was formerly incomplete and internal to organizations such as NLM. It is now formalized at the supraorganizational level by documents including Citing Medicine at Appendix A: Abbreviations for Commonly Used English Words in Journal Titles, ANSI Z39.5, ISO 4: Information and documentation -- Rules for the abbreviation of title words and titles of publications, and the ISSN.org List of Title Word Abbreviations (LTWA).
Articles not in English
As per journal articles in English:
- Forneau E, Bovet D. Recherches sur l'action sympathicolytique d'un nouveau dérivé du dioxane. Arch Int Pharmacodyn. 1933;46:178-91. French.
The NLM adds an English translation of the title enclosed in square brackets right after the title. The language is specified in full after the location (pagination), followed by a period.
- Rang HP, Dale MM, Ritter JM, Moore PK. Pharmacology. 5th ed. Edinburgh: Churchill Livingstone; 2003.
Editor(s) or compiler(s) as authors
- Beers MH, Porter RS, Jones TV, Kaplan JL, Berkwits M, editors. The Merck manual of diagnosis and therapy. 18th ed. Whitehouse Station (NJ): Merck Research Laboratories; 2006.
Authored chapter in edited publication
- Glennon RA, Dukat M. Serotonin receptors and drugs affecting serotonergic neurotransmission. In: Williams DA, Lemke TL, editors. Foye's principles of medicinal chemistry. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2002.
- Drug-interactions.com [homepage on the Internet]. Indianapolis: Indiana University Department of Medicine; 2003 [updated 17 May 2006; cited 30 May 2006]. Available from: http://medicine.iupui.edu/flockhart/
- Reference styles: Harvard and Vancouver [Retrieved 2013-03-01].
- International Committee of Medical Journal Editors (ICMJE) Uniform Requirements for Manuscripts Submitted to Biomedical Journals: Sample References, United States National Library of Medicine, retrieved 2013-03-01
- ICMJE, Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals.
- Patrias, Karen, Wendling, Dan, ed., Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers, Bethesda, Maryland, USA: United States National Library of Medicine.
- Uniform requirements for manuscripts submitted to biomedical journals. International Committee of Medical Journal Editors. BMJ (Clinical research ed.). 1991;302(6772):338–41. doi:10.1136/bmj.302.6772.338. PMID 2001512.
- Uniform requirements for manuscripts submitted to biomedical journals. International Committee of Medical Journal Editors. Canadian Medical Association Journal. 1995;152(9):1459–73. PMID 7728695.
- Uniform requirements for manuscripts submitted to biomedical journals. International Committee of Medical Journal Editors [Free full text]. Annals of Internal Medicine. 1997;126(1):36–47. PMID 8992922.
- Uniform requirements for manuscripts submitted to biomedical journals. International Committee of Medical Journal Editors. JAMA: the journal of the American Medical Association. 1997;277(11):927–34. doi:10.1001/jama.277.11.927. PMID 9062335.
- International Committee Of Medical Journal Editors (ICMJE). Uniform Requirements for Manuscripts Submitted to Biomedical Journals: writing and editing for biomedical publication [Free full text]. Haematologica. 2004;89(3):264. PMID 15020262.
- International Committee of Medical Journal Editors Uniform Requirements for Manuscripts Submitted to Biomedical Journals: Sample References [Retrieved 2006 Dec 24].
- http://library.vcc.ca/downloads/VCC_VancouverStyleGuide.pdf ""The citation in brackets is placed after any commas and periods, and before any colons and semi-colons"
- http://www.ieee.org/documents/ieeecitationref.pdf "References ... appear on the line, in square brackets, inside the punctuation."
- Patrias, K. In: Wendling, D., editor. Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers [Internet]. 2nd ed. Bethesda, MD: National Library of Medicine (US); 2007 [Retrieved 2012 February 22]. "Convert given (first) names and middle names to initials, for a maximum of two initials following each surname"
Many medical institutions maintain their own style guides, with information on how to cite sources:
- University of Queensland (PDF; accessed September 30, 2006)
- University of Leicester Library, Vancouver Style Guide (accessed 30 December 2012)