by ZHEKOV,KIRIL V.,BG, KHRISTOV,KOL'O V.,BG, NESHEV,KIRIL D.,BG, KHRISTOV,KHRISTO A.,BG, CONEV,JJORDAN C.,BG, STOJANOV,STOJAN N.,BG, TOPALOVA,DIANA I.,BG
Year of Publication 15.06.1988