@article{NSJOM_1999_29_3a_23,
     author = {M. 

 Popescu and P. Popescu},
     title = {On 

 graded algebra bundles},
     journal = {Novi Sad Journal of Mathematics},
     pages = {257-265},
     year = {1999},
     volume = {29},
     number = {3},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1999_29_3a_23/}
}