%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
%I mathdoc
%U http://geodesic.mathdoc.fr/item/AM_1999_150_3_a4/
%F AM_1999_150_3_a4