@article{NSJOM_1991_21_1a_2,
     author = {Abujabal H.A.S. and Khan M.S.},
     title = {Some commutativity 

 conditions for rings},
     journal = {Novi Sad Journal of Mathematics},
     pages = {23-31},
     publisher = {mathdoc},
     volume = {21},
     number = {1},
     year = {1991},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1991_21_1a_2/}
}