%0 Journal Article %A Changjin Xu and Qianhong Zhang %D 2011 %J International Journal of Mathematical and Computational Sciences %B World Academy of Science, Engineering and Technology %I Open Science Index 52, 2011 %T Positive Periodic Solutions in a Discrete Competitive System with the Effect of Toxic Substances %U https://publications.waset.org/pdf/15619 %V 52 %X In this paper, a delayed competitive system with the effect of toxic substances is investigated. With the aid of differential equations with piecewise constant arguments, a discrete analogue of continuous non-autonomous delayed competitive system with the effect of toxic substances is proposed. By using Gaines and Mawhin,s continuation theorem of coincidence degree theory, a easily verifiable sufficient condition for the existence of positive solutions of difference equations is obtained. %P 649 - 653