In the notation system, works are referred to in the text by numbers (eg superscripted or bracketed) and listed sequentially by number at the end of the work or the bottom of a page. The notation system can be further divided into the Vancouver system (citation–sequence – references are numbered in the list in the order they first appear in the text; or citation–name – references in the list are numbered in alphabetical order by author) and the Oxford (documentary-note) system.

The Oxford system differs from the Vancouver system in allowing each notation to include more than 1 reference, as well as, for example, explanatory information that is not essential to the text.

Many medical journals use the Vancouver system; see the International Committee of Medical Journal Editors and the National Library of Medicine (NLM) for details.