• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information

Box 76Date of publication and date of copyright

Some publications have both a date of publication and a date of copyright. A copyright date is identified by the symbol ©, the letter "c", or the word copyright preceding the date.

  • Use only the date of publication unless three or more years separates the two dates
  • In this situation, use both dates, beginning with the year of publication
  • Precede the date of copyright by the letter "c"
  • Separate the dates by a comma and a space. For example, "2002, c1997".

This convention alerts a user that the information is older than the date of publication implies.

From: Chapter 24, Databases/Retrieval Systems on the Internet

Cover of Citing Medicine
Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers [Internet]. 2nd edition.
Patrias K, author; Wendling D, editor.
Bethesda (MD): National Library of Medicine (US); 2007-.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.