Não informado. (1972). Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information.
Chicago-referens (17:e uppl.)Não informado. Abstracts of Bulgarian Scientific Literature. Sofia: Center for Scientific, Technical and Economic Information, 1972.
MLA-referens (8:e uppl.)Não informado. Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information, 1972.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.