Yearbook of National Account Statistics, 1971. New York: United Nations, 1973.
Section IV. National Security
Baldwin, Godfrey (ed.). International Population Reports. (U.S. Department of Commerce, Series p-91, No. 18.) Washington: GPO, 1969.
Bulgaria. State Information Office with the Council of Ministers. Statistical Pocket Book 1970. Sofia: Sofia Press, 1970.
Cary, William. Bulgaria Today. New York: Exposition Press, 1965.
Dellin, L. A. D. (ed.) Bulgaria: East-Central Europe Under the Communists. New York: Praeger, 1957.
The Military Balance, 1972-73. London: Institute for Strategic Studies, 1972.
Newman, Bernard. Bulgarian Background. London: Robert Hale, 1961.
Oren, Nissan. Bulgarian Communism. New York: Columbia University Press, 1971.
Perl, Lila. Yugoslavia, Romania, Bulgaria. Camden: Thomas Nelson, 1970.