@article{NSJOM_2014_44_2a_11,
     author = {J.Jagan Mohan},
     title = {Variation of parameters for nabla

 fractional difference equations},
     journal = {Novi Sad Journal of Mathematics},
     pages = {149-159},
     publisher = {mathdoc},
     volume = {44},
     number = {2},
     year = {2014},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_2014_44_2a_11/}
}