%0 Journal Article
%A Rival, Ivan
%A Sands, Bill
%T Planar Sublattices of a Free Lattice. I
%J Canadian journal of mathematics
%D 1978
%P 1256-1283
%V 30
%N 6
%U http://geodesic.mathdoc.fr/articles/10.4153/CJM-1978-104-2/
%R 10.4153/CJM-1978-104-2
%F 10_4153_CJM_1978_104_2