Existence of periodic solution for a class of neutral differential   equations with impulses
  By applying a Mawhin's continuation theorem of coincidence degree theory, we establish sufficient conditions for the existence of a periodic solution for a class of impulsive neutral differential equations. The procedure adopted in this work makes use of a non-impulsive associated equation in order to overcome the difficulties resulting from the moments of impulse effects. Under particular assumptions this solution is continuously differentiable on each interval with no impulse effect. 
Suzete M. Afonso and Andr\'e L. Furtado
math.CA math.FA