URN:NBN:SI:DOC-2NPND4BH2011documents/doc/2/URN_NBN_SI_doc-2NPND4BH_001.htmdocuments/doc/2/URN_NBN_SI_doc-2NPND4BH_001.pdfdocuments/doc/2/URN_NBN_SI_doc-2NPND4BH_001.txtdocuments/doc/2/URN_NBN_SI_doc-2NPND4BH_001.xml116149journal157067132232-2094URN:NBN:SI:doc-2NPND4BHengUniversity of Ljubljana Institute of Mathematics, Physics and Mechanics Department of MathematicsPreprint series (Ljubljana)InC