The latest version of the latter is Citing Medicine, per the References > Style and Format section of the ICMJE Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals.
A narrower definition of the Vancouver system refers to a specific author–number format specified by the ICMJE Recommendations (Uniform Requirements for Manuscripts, URM).
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).
[10] 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.
[4] References are numbered consecutively in order of appearance in the text – they are identified by Arabic numerals in parentheses (1), square brackets [1], superscript1, or a combination[1].
The number usually appears at the end of the material it supports, and an entry in the reference list would give full bibliographical information for the source: Blood loss and the number of patients requiring post-operative blood transfusions were significantly greater, but operation and fluoroscopy times were significantly shorter, for the DHS versus the PFNA group[1].And the entry in the reference list would be: Several descriptions of the Vancouver system say 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.
)[15] 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.
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): Optionally, a unique identifier (such as the article's DOI or PMID) may be added to the citation: NLM elides ending page numbers and uses a hyphen as the range indicating character (184-5).
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 omits the year from its normal location after the journal title abbreviation if there is no print data to give (online-only publication).