Não informado. (1972). Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Abstracts of Bulgarian Scientific Literature. Sofia: Center for Scientific, Technical and Economic Information, 1972.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information, 1972.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.