%0 Journal Article %T Errata %J Canadian mathematical bulletin %D 1978 %P 508-508 %V 21 %N 4 %U http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-088-4/ %R 10.4153/CMB-1978-088-4 %F 10_4153_CMB_1978_088_4