College of Mathematics and Computer Science, Fuzhou University, Fuzhou 350002, P.R. China. E-mail:
In this paper, by using Mawhin coincidence degree, we study the global existence of positive periodic solutions for a class of mutualism systems with several delays and obtain a new and interesting criterion, which is much different from those of Yang etc. [8]. Moreover, our arguments for obtaining bounds of solutions to the operator equation Lx = λN x are much different from those used in [8]. So some new arguments are employed for the first time.
Periodic solutions, coincidence degree, mutualism model
