APA (7th ed.) Citation

Antonov, A., Antonova, V., & Penčeva, M. (1991). History of Bulgaria: From antiquity to present days. May.

Chicago Style (17th ed.) Citation

Antonov, Alexandăr, Valentina Antonova, and Majja Penčeva. History of Bulgaria: From Antiquity to Present Days. Sofia: May, 1991.

MLA (9th ed.) Citation

Antonov, Alexandăr, et al. History of Bulgaria: From Antiquity to Present Days. May, 1991.