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 Existence of Nonoscillatory Solutions for System of Fractional Differential Equations with Positive and Negative Coefficients Youjun Liu,Huanhuan Zhao,Huiqin Chen,Shugui Kang Keywords:System; Fractional differential equation; Liouville derivative; Positive and negative coefficients; Nonoscillatory solutions. Abstract: In this paper we consider the system of fractional differential equations with positive and negative coefficients. We use the $Banach$ contraction principle to obtain new sufficient conditions for the existence of nonoscillatory solutions.