Existence of 2n Positive Periodic Solutions to n-Species Nonautonomous Food Chains with Harvesting Terms

By using Mawhin's continuation theorem of coincidence degree theory and some skills of inequalities, we establish the existence of at least 2n positive periodic solutions for n-species nonautonomous Lotka-Volterra type food chains with harvesting terms. An example is given to illustrate the effectiveness of our results.