Anderson, Raymond H. "Bulgarians Like Zip in Wash Cycle," New York Times, May 21, 1973, 7.
Apanasewicz, Nellie, and Rosen, Seymour M. Studies in Comparative Education. (OE-14115.) Washington: U.S. Department of Health, Education and Welfare, 1965.
Baldwin, Godfrey (ed.). International Population Reports. (U.S. Department of Commerce, Series P-91, No. 18.) Washington: GPO, 1969.
"Big Prospects for Education," Bulgaria Today [Sofia], XX, No. 8, August 1971, 6.
Blumenfeld, Yorick. Seesaw: Cultural Life in Eastern Europe. New York: Harcourt, Brace and World, 1968.
Brown, James F. Bulgaria Under Communist Rule. New York: Praeger, 1970.
Bulgaria. State Information Office with the Council of Ministers. Statistical Pocket Book 1970. Sofia: Sofia Press, 1970.
"Bulgaria: History." Pages 385-400 in Encyclopaedia Britannica, IV. Chicago: William Benton, 1969.
"Bulgaria." Pages 41-50 in Moshe Sachs (ed.), Worldmark Encyclopedia of the Nations, V: Europe. New York: Harper and Row, 1967.
"Bulgaria." Pages 225-233 in World Survey of Education, V. Paris: United Nations Educational, Scientific and Cultural Organization, 1971.