Positive Periodic Solutions of N-Species Neutral Delay Systems

In this paper, we employ some new techniques to study the existence of positive periodic solution of n-species neutral delay system Ni′ = Ni(t)[αi(t) — \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\sum\limits_{j = 1}^n {\beta _{ij} } $$ \end{document}βij(t)Nj(t) — \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\sum\limits_{j = 1}^n {b_{ij} } $$ \end{document}bij(t)Nj(t—τij(t))—\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\sum\limits_{j = 1}^n {c_{ij} } $$ \end{document}cij(t)Nj′(t—τij(t))].