[1] Department of Finance,
[2] Nowy Sa¸cz Graduate School of Business – NLU,undefined
[3] Zielona 27,undefined
[4] 33-300 Nowy Sa¸cz,undefined
[5] Poland (e-mail: capinski@wsb-nlu.nowy-sacz.pl),undefined
[6] Department of Mathematics,undefined
[7] University of Hull,undefined
[8] Hull,undefined
[9] HU6 7RX,undefined
[10] England (e-mail: N.J.Cutland@maths.hull.ac.uk),undefined