@article{NSJOM_1975_5_Nonea_1,
     author = {Stankovi\'c 

 Bogoljub},
     title = {On a class of operators},
     journal = {Novi Sad Journal of Mathematics},
     pages = {9-12},
     publisher = {mathdoc},
     volume = {5},
     year = {1975},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1975_5_Nonea_1/}
}