1. Dewar MJS, Longuet-Higgins HC (1952) Proc Roy Soc London A214: 482
2. Gutman I (1974) Croat Chem Acta 46: 209
3. Gutman I, Cyvin SJ (1989) Introduction to the theory of benzenoid hydrocarbons, Springer, Berlin Heidelberg New York
4. Merrifield RE, Simmons HE (1989) Topological methods in chemistry, Wiley, New York
5. Topics in Current Chemistry,1990