Gordon, C. M.; Litherland, R. A.; and Murasugi, K. "Signatures of Covering Links." Canad. J. Math.33, 381-394, 1981.Murasugi, K. "On the Signature of Links." Topology9, 283-298, 1970.Murasugi, K. "Signatures and Alexander Polynomials of Two-Bridge Knots." C. R. Math. Rep. Acad. Sci. Canada5, 133-136, 1983.Murasugi, K. "On the Signature of a Graph." C. R. Math. Rep. Acad. Sci. Canada10, 107-111, 1988.Murasugi, K. "On Invariants of Graphs with Applications to Knot Theory." Trans. Amer. Math. Soc.314, 1-49, 1989.Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, 1976.Stoimenow, A. "Signatures." http://www.ms.u-tokyo.ac.jp/~stoimeno/ptab/sig10.html.