Abstract
Sufficient conditions have been obtained for the existence of at least two non-negative periodic solutions to a system of first-order nonlinear functional differential equations. Applications to some ecological models are given.
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Acknowledgements
This work is supported by National Board for Higher Mathematics, Department of Atomic Energy, Government of India, under sponsored research scheme vide grant no. 48/5/2006-R&D-II/1350 dated 26.02.2007.