Title: Some extensions of the Massera Theorem to three 
dimensional monotone dynamical systems. 

Abstract: In this talk we are going to generalize the Massera 
theorem to three dimensions. This theorem states the existence 
of a periodic solution if there exists a bounded one. 
Although this theorem is specific for two dimensions we 
prove this theorem assuming that the return 
map has some kind of monotone propeties. We also apply this 
theorem to some specific situations.