TY - JOUR AU - Zeng, Zhijun TI - Existence of positive periodic solutions for a class of nonautonomous difference equations JO - Electronic Journal of Differential Equations PY - 2006 VL - 2006 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/EJDE_2006__2006__a88/ LA - en ID - EJDE_2006__2006__a88 ER -