  In this paper, we consider sublinear second order differential equations with
impulsive effects. Basing on the Poincar\'{e}-Bohl fixed point theorem, we
first will prove the existence of harmonic solutions. The existence of
subharmonic solutions is also obtained by a new twist fixed point theorem
recently established by Qian etc in 2015 (\cite{Qian15}).

Classical Analysis and ODEs