TY - JOUR AU - Sun, Juntao AU - Chu, Jifeng TI - Necessary and sufficient conditions for the existence of periodic solution to singular problems with impulses JO - Electronic Journal of Differential Equations PY - 2014 VL - 2014 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/EJDE_2014__2014__a38/ LA - en ID - EJDE_2014__2014__a38 ER -