Specific Rules #5 for Date of Publication (required) to Citing Entire Reports Vancouver Style: No date of publication can be found

Reports by US government agencies are not copyrighted, but reports issued by the agencies of other countries and those published by performing organizations may be copyrighted.

If no date of publication can be found, but the publication contains a date of copyright, use the date of copyright preceded by the letter "c"; for example c2005.

Plymouth Meeting (PA): ECRI; c2005.

Washington: Urban Institute; c2004.

If neither a date of publication nor a date of copyright can be found, but a date can be estimated because of material contained in the report or in accompanying material, insert a question mark after the estimated date and place date information in square brackets.

Los Angeles (CA): California Student Health Project; [1967?].

Según:

Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers [Internet]. 2nd edition. Chapter 4: Scientific and Technical Reports