Columbia subject headings:
Bŭlgarska komunisticheska partii︠a︡--History--Sources.
Bŭlgarska rabotnicheska sot︠s︡ialdemokraticheska partii︠a︡--History--Sources.
Harvard subject headings:
Bŭlgarska komunisticheska partii︠a︡--History--Sources.
Bŭlgarska rabotnicheska sot͡sialdemokraticheska partii͡a--History--Sources.
Bŭlgarska rabotnicheska sot︠s︡ial-demokraticheska partii︠a︡--History--Sources.
Princeton subject headings:
Bŭlgarska rabotnicheska sot︠s︡ial-demokraticheska partii︠a︡--History--Sources.