1. For introductory concepts of graph theory see: Introduction to Graph Theory, Academic Press, New York, 1972
2. Graphs as Mathematical Models, Prindle, Weber and Schmidt, Boston, 1977, or some other introductory text.
3. and in Selected Topics in Graph Theory, and Eds., Academic Press, New York, 1978, pp. 275-307
4. in Graphs and Combinatorics, and Eds., Springer, Berlin, 1974, p. 153