Não informado. (1962). Abstracts of bulgarian scientific literature. Center for Scientific, Technical and Economic Information.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Abstracts of Bulgarian Scientific Literature. Sofia: Center for Scientific, Technical and Economic Information, 1962.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Abstracts of Bulgarian Scientific Literature. Center for Scientific, Technical and Economic Information, 1962.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.