TY - JOUR AU - Raffoul, Youssef N. TI - Positive periodic solutions of nonlinear functional difference equations JO - Electronic Journal of Differential Equations PY - 2002 VL - 2002 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/EJDE_2002__2002__a73/ LA - en ID - EJDE_2002__2002__a73 ER -