Não informado. (1972). Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information.
Chicago-Zitierstil (17. Ausg.)Não informado. Abstracts of Bulgarian Scientific Literature. Sofia: Center for Scientific, Technical and Economic Information, 1972.
MLA-Zitierstil (8. Ausg.)Não informado. Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information, 1972.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.