Serdica Mathematical Journal, founded: 1975, published quarterly by the Institute of Mathematics and Informatics.
Serdica Journal of Computing, published by the Institute of Mathematics and Informatics.
PLISKA Studia Mathematica Bulgarica.
MATHEMATICA BALKANICA, founded: New Series, 1987, published quarterly.
PHYSICO-MATHEMATICAL JOURNAL, founded: 1904, published quarterly.
East Journal on Approximations (site in New Zealand).
Mathematics and Informatics Quarterly (site in The Netherlands).