Não informado. (1972). Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Annals of the Research Institute of Epidemiology and Microbiology. Sofia: Ministery of Public Health, 1972.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Annals of the Research Institute of Epidemiology and Microbiology. Ministery of Public Health, 1972.
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