[1] Johannes Kepler Univ Linz, Dept Algebra Stochast & Knowledge Based Math Syst, Fuzzy Log Lab, A-4040 Linz, Austria
[2] Slovak Univ Technol Bratislava, Fac Civil Engn, Dept Math & Descript Geometry, Bratislava 81368, Slovakia
[3] Acad Sci Czech Republ, Inst Informat Theory & Automat, CR-18208 Prague, Czech Republic
[4] Univ Novi Sad, Dept Math & Informat, YU-21000 Novi Sad, Serbia