Specific Rules #6 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: No date of publication or copyright can be found

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

Bombay: Cardiological Society of India; [1980?].

If neither a date of publication nor a date of copyright can be found nor can the date be estimated, use [date unknown]:

Bologna (Italy): Malipiero S.p.A. Editore; [date unknown].

Según:

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

Related:

General Rules for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style

Specific Rules #1 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Multiple years of publication

Specific Rules #2 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Non-English names for months

Specific Rules #3 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Seasons instead of months

Specific Rules #4 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Date of publication and date of copyright

Specific Rules #5 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: No date of publication, but a date of copyright

Specific Rules #6 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: No date of publication or copyright can be found

Specific Rules #7 for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Options for date of publication

Examples for Date of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style