Não informado. (1972). Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information.
Čikaški stil citiranja (17. izdanje)Não informado. Abstracts of Bulgarian Scientific Literature. Sofia: Center for Scientific, Technical and Economic Information, 1972.
MLA način citiranja (8. izdanje)Não informado. Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information, 1972.
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