%0 Journal Article %A C.A. Boyd %T RESIDUATION IN SEMIGROUPS OF PRE-CLOSURES. %J Semigroup forum %D 1975 %P 328-336 %V 11 %I mathdoc %U http://geodesic.mathdoc.fr/item/SF_1975__11_134147/ %G en %F SF_1975__11_134147