%0 Journal Article %A Mario Gionfriddo %T Partial parallel classes in Steiner systems %J Colloquium Mathematicum %D 1989 %P 221-227 %V 57 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/cm-57-2-221-227/ %R 10.4064/cm-57-2-221-227 %G en %F 10_4064_cm_57_2_221_227