%0 Journal Article
%A Neil Robertson
%A P.D. Seymour
%A Robin Thomas
%T Permanents, Pfaffian orientations, and even directed circuits
%J Annals of mathematics
%D 1999
%V 150
%N 3
%U http://geodesic.mathdoc.fr/articles/10.2307/121059/
%R 10.2307/121059
%F 10_2307_121059