P.J. Davis, Circulant Matrices, Wiley, New York, 1979.
 K.A. Germina and T. Zaslavsky, On products and line graphs of signed graphs, their eigenvalues and energy, Linear Algebra Appl. 435 (2011), no. 10, 2432–2450.
 Shahul K. Hameed, T.V. Shijin, P. Soorya, K.A. Germina, and T. Zaslavsky, Signed distance in signed graphs, Linear Algebra Appl. 608 (2021), 236–247.
 F. Harary, Graph Theory, Addison-Wesley Publishing Co., 1969.
 K. Shahul Hameed and K. Germina, On composition of signed graphs, Discuss. Math. Graph Theory 32 (2012), no. 3, 507–516.
 T.V. Shijin, P. Soorya, K Shahul Hameed, and K.A. Germina, On distance compatibility in product of signed graphss, (communicated).
 T. Zaslavsky, Six signed petersen graphs, and their automorphisms, Discrete Math. 312 (2012), no. 9, 1558–1583.
 F. Zhang, Matrix Theory: Basic Results and Techniques, Springer–Verlag, 1999.