Ivanov, Ivan Ganchev, Ivan Ganchev Ivanov, Prof. DSci. Head, Department of Statistics and Econometrics, Faculty of Economics and Business Administration, Sofia University "St. Kl. Ohridski" 1113 Sofia, 125 Tsarigradsko Shosse Blvd., bl.3, Bulgaria <i_ivanov@feb.uni-sofia.bg>, Bulgaria