@article{NSJOM_2005_35_2a_4,
     author = {J. M. Rassias},
     title = {On the {Ulam} problem for {Euler} 

 quadratic mappings},
     journal = {Novi Sad Journal of Mathematics},
     pages = {57-66},
     publisher = {mathdoc},
     volume = {35},
     number = {2},
     year = {2005},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_2005_35_2a_4/}
}