Columbia subject headings:
Harvard subject headings:
Bulgaria--Foreign relations--1944-
Bulgaria--Foreign relations--1944-1990.
Conference on Security and Cooperation in Europe (1972 : Helsinki, Finland)
Conference on Security and Cooperation in Europe (1975 : Helsinki, Finland)
Princeton subject headings:
Bulgaria--Foreign relations--1944-1990.
Conference on Security and Cooperation in Europe (1975 : Helsinki, Finland)