Birkhoff's theorem states:


*The set of $n \times n$ doubly stochastic matrices is a convex set whose extreme points are the permutation matrices*


This theorem seems to be commonly attributed to Birkhoff (perhaps also von Neumann). But I recall listening to a talk by Harold Kuhn, where he said that this theorem should actually be attributed to some $P$ where $P \in \{$Jacobi, Dénes Kőnig, Jenő Egerváry, Somebody else?$\}$.


**Question**: Does anybody know whom Kuhn might have meant, and to whom this theorem should really be attributed? 


I would be very happy to learn the connection (also, yes, am embarrassed that despite listening carefully during the talk, I have still forgotten!)



Birkhoff's theorem about doubly stochastic matrices
See the [Wikipedia page](http://en.wikipedia.org/wiki/Birkhoff_polytope) for the Birkhoff polytope. It says that equivalent results were obtained by Steinitz in 1894 and by Kőnig in 1916.


