Biggs, Norman. Discrete Mathematics. Rev. ed. Oxford: Clarendon, 1989. Print.
Grimaldi, Ralph P. Discrete and Combinatorial Mathematics: An Applied Introduction. Fifth edition. Harlow, Essex, England: Pearson Education Limited, 2014. Web. <https://www.vlebooks.com/vleweb/product/openreader?id=AberystUni&isbn=9781292035994>.
Liu, C. L. Elements of Discrete Mathematics. 2nd ed. McGraw-Hill computer science series. New York: McGraw-Hill, 1985. Print.
Wilson, Robin J., and John J. Watkins. Graphs: An Introductory Approach: A First Course in Discrete Mathematics. New York: Wiley, 1990. Print.
