Contacte-mail: sjaksic at uns ac rs Phone: +381 21 4852288 Fax: +381 21 6350770 web: http://imft.ftn.uns.ac.rs/~svetlana/ | AddressChair for Mathematics Center for Mathematics and Statictics Department for Fundamental Disciplines Faculty of Technical Sciences University of Novi Sad 21000 Novi Sad Serbia |  |