TY - JFULL AU - Changjin Xu and Qianhong Zhang PY - 2011/5/ TI - Positive Periodic Solutions in a Discrete Competitive System with the Effect of Toxic Substances T2 - International Journal of Mathematical and Computational Sciences SP - 648 EP - 653 VL - 5 SN - 1307-6892 UR - https://publications.waset.org/pdf/15619 PU - World Academy of Science, Engineering and Technology NX - Open Science Index 52, 2011 N2 - 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. ER -