Eight positive periodic solutions to three species non-autonomous Lotka-Volterra cooperative systems with harvesting terms (Q648534)

The authors consider a three-species Lotka-Volterra cooperative model with periodic coefficients and harvesting terms. They establish conditions on these periodic data that allow to prove the existence of eight positive periodic solutions. The key tools for the proof are Mawhin's version of the theory of coincidence degree, and some elementary linear algebraic inequalities. As a whole, the proof is very elegant and turns out to be much simpler than a recent proof yielding only four periodic solutions. Finally, the authors present an explicit illustrative example.