Permanence of an NN-species cooperation system with continuous time delays and feedback controls

In this paper, we consider an NN-species cooperation system with continuous time delays and feedback controls. By applying a new integral inequality, we obtain a set of sufficient conditions which ensure the permanence of the system. Our result shows that feedback control variables have no influence on the permanence of the system, thus improving the corresponding results of Chen, Liao and Huang [F.D. Chen, X.Y. Liao, Z.K. Huang, The dynamic behavior of NN-species cooperation system with continuous time delays and feedback controls, Applied Mathematics and Computation 181 (2) (2006) 803–815].