Chiefly in Bulgarian; some French.
Summaries in Bulgarian, English, French, and/or German.
Issued by Bŭlgarska akademii︠a︡ na naukite.
Formed by the union of: Izvestii︠a︡ na Geologicheskii︠a︡ institut. Serii︠a︡ Paleontologii︠a︡, and: Izvestii︠a︡ na Geologicheskii︠a︡ institut. Serii︠a︡ Stratigrafii︠a︡ i litologii︠a︡.