In 1937 there appeared a paper that was to have a profound influence on
the progress of combinatorial enumeration, both in its theoretical and
applied aspects. Entitled Kombinatorische Anzahlbest- immungen jUr
Gruppen, Graphen und chemische Verbindungen, it was published in Acta
Mathematica, Vol. 68, pp. 145 to 254. Its author, George Polya, was
already a mathematician of considerable stature, well-known for
outstanding work in many branches of mathematics, particularly analysis.
The paper in Question was unusual in that it depended almost entirely on
a single theorem -- the "Hauptsatz" of Section 4 -- a theorem which gave
a method for solving a general type of enumera- tion problem. On the
face of it, this is not something that one would expect to run to over
100 pages. Yet the range of the applica- tions of the theorem and of its
ramifications was enormous, as Polya clearly showed. In the various
sections of his paper he explored many applications to the enumeration
of graphs, principally trees, and of chemical isomers, using his theorem
to present a comprehen- sive and unified treatment of problems which had
previously been solved, if at all, only by ad hoc methods. In the final
section he investigated the asymptotic properties of these enumerational
results, bringing to bear his formidable insight as an analyst.