[1] Univ West Bohemia, Fac Appl Sci, Dept Math, Tech 8, Plzen 30614, Czech Republic
[2] Univ West Bohemia, Fac Appl Sci, European Ctr Excellence NTIS New Technol Informat, Tech 8, Plzen 30614, Czech Republic
[3] Vienna Univ Technol, Inst L & Computat, Algorithms & Complex Grp, Favoritenstr 9-11, A-1040 Vienna, Austria