
Another short proof of the JoniRotaGodsil integral formula for counting bipartite matchingsAbstract: How many perfect matchings are contained in a given bipartite graph? An exercise in Godsil's 1993 extit{Algebraic Combinatorics} solicits proof that this question's answer is an integral involving a certain rook polynomial. Though not widely known, this result appears implicitly in Riordan's 1958 extit{An Introduction to Combinatorial Analysis}. It was stated more explicitly and proved independently by S.A.~Joni and G.C.~Rota [ extit{JCTA} extbf{29} (1980), 5973] and C.D.~Godsil [ extit{Combinatorica} extbf{1} (1981), 257262]. Another generation later, perhaps it's time both to simplify the proof and to broaden the formula's reach.
