"National Revival Architecture," Bulgaria Today [Sofia], XXI, No. 7, July 1972, 16-17.
"The New Architecture," East Europe, XIV, No. 4, April 1965, 7-15.
Newman, Bernard. Bulgaria Background. London: Robert Hale, 1961.
Olson, Kenneth E. The History Makers. Baton Rouge: Louisiana State University Press, 1966.
Oren, Nissan. Bulgarian Communism. New York: Columbia University Press, 1971.
——. Revolution Administered: Agrarianism and Communism in Bulgaria. Baltimore: Johns Hopkins University Press, 1973.
Oshavkov, Zhivko. "Religious Belief in Bulgaria," Bulgaria Today [Sofia], XVI, No. 10, October 1967, 20-22.
Parkin, Frank. Class Inequality and Political Order. New York: Praeger, 1971.
Perl, Lila. Yugoslavia, Romania, Bulgaria. Camden: Thomas Nelson, 1970.
Petrov, Staian. The Struggle of the Bulgarian Communist Party to Organize the Social Basis of the Revolution. Sofia: Sofia Press, 1970.