Bulgarian winter competitions in Mathematics, Informatics and Mathematical Linguistics Svetoslav J. Bilchev; P. Kenderov — 2001 Μαθηματική Επιθεώρηση
A new Logistical Approach to Management of Export/Import Operations in a National Economics. Panayiotis M. Vlamos; Svetoslav J. Bilchev; Valery V. Bokov — 2000 Μαθηματική Επιθεώρηση