Não informado. (1978). Abstracts of bulgarian scientific literature. Central Institute for Scientific, Technical and Economic Information.
Chicago-referens (17:e uppl.)Não informado. Abstracts of Bulgarian Scientific Literature. Sofia: Central Institute for Scientific, Technical and Economic Information, 1978.
MLA-referens (8:e uppl.)Não informado. Abstracts of Bulgarian Scientific Literature. Central Institute for Scientific, Technical and Economic Information, 1978.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.