[1] Univ Zagreb, Fac Civil Engn, Zagreb 10000, Croatia
[2] Univ Zagreb, Dept Math, Zagreb 10000, Croatia
[3] Rudjer Boskovic Inst, NMR Ctr, Zagreb 10000, Croatia
[4] Univ Split, Fac Sci, Split 21000, Croatia
[5] Univ Dubrovnik, IMC, Dubrovnik 20000, Croatia
[6] Univ Kragujevac, Fac Sci, Kragujevac 34000, Serbia