"Statistics on Rising Living Standard Given," Naruchnik na Agitatore, Sofia, No. 24, December 1972. (JPRS 58,480, No. 851, 1973).
"Status Prospects of Medical Science Discussed," Zdraven Front, Sofia, April 24, 1971. (JPRS 53,482, No. 375, 1971).
"Study of Services in Burgas Area Reviewed," Narodni Suveti, Sofia, No. 1, 1970. (JPRS 50,150, No. 197, 1970).
U.S. Department of State. Bureau of Intelligence and Research. Educational and Cultural Exchanges Between Communist and Non-Communist Countries in 1970. (Research Study RSES-34.) Washington: 1971.
U.S. Department of State. Bureau of Public Affairs. Office of Media Services. "Educational and Cultural Exchange Between Communist and Non-Communist Countries in 1971." (News Release.) December 8, 1972.
U.S. Department of State. Geographer. Office of Research in Economics and Science. Bulgaria-Greece Boundary. (International Boundary Study, No. 56). Washington: 1965.
Wolff, Robert Lee. The Balkans in Our Time. Cambridge: Harvard University Press, 1956.
World Christian Handbook, 1968. (Eds., H. Wakelin Coxill and Kenneth G. Grubb.) New York: Abingdon Press, 1967.
World of Learning, 1972-73. London: Europa Publications, 1973, 207-212.
World Population Data Sheet, 1972. Washington: Population Reference Bureau, 1972.