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Bartłomiej Jefmański
Wrocław University of Economics Faculty of Economics, Management and Tourism Department of Econometrics and Computer Science Nowowiejska 3, 58-500 Jelenia Góra, Poland
Krzysztof Błoński
University of Szczecin Faculty of Economics and Management Marketing Department Mickiewicza 64, 71-101 Szczecin, Poland