Specific Rules #4 for Place of Publication (required) to Citing Conference Proceedings Vancouver Style: No place of publication can be found

If no place of publication can be found on the title page or the verso (back) of the title page, 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]".

Palulonis RM, editor. 19th Conference on the Medical Aspects of Sports; 1977; San Francisco, CA. [Chicago]: American Medical Association; c1978. 75 p.

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

2nd Annual Meeting of the Indian Leptospirosis Society (ILS); 2001 May 12-13; Cochin, India. [place unknown]: Indian Leptospirosis Society; 2001. 70 p.

Según:

Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers [Internet]. 2nd edition. Chapter 3: Conference Publications

Related:

General Rules for Place of Publication (required) to Citing Conference Proceedings Vancouver Style

Specific Rules #1 for Place of Publication (required) to Citing Conference Proceedings Vancouver Style: Optional inclusion of institution where conference was held

Specific Rules #2 for Place of Publication (required) to Citing Conference Proceedings Vancouver Style: Non-US cities

Specific Rules #3 for Place of Publication (required) to Citing Conference Proceedings Vancouver Style: Multiple places of publication

Specific Rules #4 for Place of Publication (required) to Citing Conference Proceedings Vancouver Style: No place of publication can be found

Example Entries for Place of Publication (required) to Citing Conference Proceedings Vancouver Style