Columbia subject headings:
Architecture--Bulgaria--Sofia--Guidebooks.
Architecture--Bulgaria--Sofia--History--Guidebooks.
Sofia (Bulgaria)--Buildings, structures, etc.--Guidebooks.
Harvard subject headings:
Architecture--Bulgaria--Sofia--Guidebooks.
Architecture--Bulgaria--Sofia--History--Guidebooks.
Sofia (Bulgaria)--Buildings, structures, etc.--Guidebooks.
Princeton subject headings:
Architecture--Bulgaria--Sofia--Guidebooks.
Guidebooks.
Sofia (Bulgaria)--Buildings, structures, etc.--Guidebooks.