Não informado. (1972). Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health.
Chicago-referens (17:e uppl.)Não informado. Annals of the Research Institute of Epidemiology and Microbiology. Sofia: Ministery of Public Health, 1972.
MLA-referens (8:e uppl.)Não informado. Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health, 1972.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.