Positive Periodic Solution of a Periodic Cooperative Model with State Dependent Delays

By using the continuation theorem of coincidence degree theory, sufficient conditions are obtained for the existence of positive periodic solution for the periodic cooperative system with state dependent delays where r_i, a_i, c_i, i = 1, 2 are positive continuous -periodic functions, b_i, i = 1, 2 are nonnegative continuous -periodic functions, and _ij, i = 1, 2; j = 1, 2, 3 are nonnegative continuous functions and -periodic with respect to their first argument.