@article{EJDE_2002__2002__a73,
     author = {Raffoul,  Youssef N.},
     title = {Positive periodic solutions of nonlinear functional difference equations},
     journal = {Electronic journal of differential equations},
     year = {2002},
     volume = {2002},
     zbl = {1007.39005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2002__2002__a73/}
}