[1] C. Adiga, R. Balakrishnan and W. So, The skew energy of a digraph, Linear Algebra Appl., 432 (2010) 1825–1835.
[2] T. M. Apostol, Introduction to analytic number theory, Undergraduate Texts in Mathematics, Springer-Verlag, New York-Heidelberg, 1976.
[3] R. B. Bapat, J. W. Grossman and D. M. Kulakarni, Generalized matrix tree theorem for mixed graphs, Linear and Multilinear Algebra, 46 (1999) 299–312.
[4] R. B. Bapat, J. W. Grossman and D. M. Kulakarni, Edge version of the matrix tree theorem for trees, Linear and Multilinear Algebra, 47 (2000) 217–229.
[5] P. J. Davis, Circulant Matrices, A Wiley-Interscience Publication, Pure and Applied Mathematics, John Wiley
Sons, New York-Chichester-Brisbane, 1979.
[6] W. Klotz and T. Sander, Some properties of unitary Cayley graphs, Electron. J. Combin., 14 (2007) 1–12.
[7] F. Yizheng, On spectra integral variations of mixed graph, Linear Algebra Appl., 374 (2003) 307–316.
[8] I. Gutman, The energy of a graph, Ber. Math. Statist. sekt. Forsch. Graz, 103 (1978) 1–22.
[9] L. S. Melnikov and V. G. Vizing, The edge chromatic number of a directed/mixed multigraph, J. Graph Theory, 31 (1999) 267–273.
[10] H. N. Ramaswamy and C. R. Veena, On the energy of unitary Cayley graphs, Electron. J. Combin., 16 (2009) 1–8.
[11] X. D. Zhang and J. S. Li, The Laplacian spectrum of a mixed graph, Linear Algebra Appl., 353 (2002) 11–20.
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