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{\bf Yaoping Hou  and Tiangang Lei}
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{\bf Characteristic Polynomials of Skew-Adjacency Matrices of Oriented Graphs}
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An oriented graph $\overleftarrow{G}$ is a simple  undirected graph $G$ with an orientation, which assigns  to each edge a direction so that $\overleftarrow{G}$ becomes a directed graph. $G$ is called the underlying graph of $\overleftarrow{G}$ and we denote by  $S(\overleftarrow{G})$  the skew-adjacency matrix  of $\overleftarrow{G}$ and its spectrum $Sp(\overleftarrow{G})$ is called the skew-spectrum of $\overleftarrow{G}$. 
 In this paper,  the coefficients of the characteristic  polynomial  of the skew-adjacency  matrix $S(\overleftarrow{G}) $ are given in terms of $\overleftarrow{G}$ and as its applications,  new combinatorial proofs of known results  are obtained and  new families of  oriented bipartite graphs $\overleftarrow{G}$ with $Sp(\overleftarrow{G})={\bf i} Sp(G) $  are given. 

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