@article{NSJOM_1978_8_Nonea_10,
     author = {Bogdanovi\'c 

 Stojan and Crvenkovi\'c Sini\v{s}a},
     title = {On some classes of 

 semigroups},
     journal = {Novi Sad Journal of Mathematics},
     pages = {69-77},
     publisher = {mathdoc},
     volume = {8},
     year = {1978},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1978_8_Nonea_10/}
}