THE EXPLOSIVE GROWTH OF GRAPH THEORY

The first book on graph theory as a separate subject in mathematics was written by Konig [ll] in 1936. He wrote in German because he correctly decided that if it were written in his native Hungarian, very few people would be able to read it. This book was reprinted in the United States in 1950. When I first became interested in graph theory in September 1950, this was the only book available on the subject. There were some theorems on graphs in the pioneering book on topology by Veblen [15] whose first chapter takes up “linear graphs.” There were also some booklets by Lucas and Saint&-Lague, referenced in Konig’s book, on the use of graphs in solving puzzles and in recreational mathematics. There were in 1950 literally only about a dozen mathematicians in the world actively doing research in graph theory! The second book on graph theory, by Berge [l], appeared in French in 1958. I had begun working on a book on graph theory since 1950, virtually the moment I was exposed to this fascinating aesthetic art form. As I was writing each chapter, so many tractable open questions suggested themselves that research impeded the process of writing. For this reason, my book [ 101 did not appear until 1969. CHART 1 displays the number of books which dealt with either graph theory as a separate subject, some special topic in graph theory, or a particular application of graph