Specific Rules #4 for Place of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: No place of publication can be found

If no place of publication can be found on the title page or its verso (back), but one can be found elsewhere in the publication or can be reasonably inferred (e.g., Chicago as the place for a publication of the American Medical Association), place the city in square brackets, such as "[Chicago]".

If no place of publication can be found or inferred, use [place unknown].

[place unknown]: Hoobler; 1991.

Según:

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

Related:

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

Specific Rules #1 for Place of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Non-US cities

Specific Rules #2 for Place of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Joint publication

Specific Rules #3 for Place of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: Multiple places of publication

Specific Rules #4 for Place of Publication (required) for the Volume for Individual Volumes With a Separate Title and Separate Authors/Editors Vancouver Style: No place of publication can be found

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