Izvestiya S''yuza na Uchenite - Ruse. Kniga 5, Matematika, Informatika, Fizika. Proceedings of the Union of Scientists - Ruse. Book 5, Mathematics, Informatics and Physics. Union of Scientists (S''yuza na Uchenite), Ruse.
Journal, ISSN 1311-9184
http://suruse.uni-ruse.bg/proceedings/bul/Math_bg.htm
No longer indexed.
