%0 Journal Article %A Félix de Delgado de la Manta %T Groenstein curves and symmetry of the semigroup of values. %J Manuscripta mathematica %D 1988 %P 285-296 %V 61 %N 4 %I mathdoc %U http://geodesic.mathdoc.fr/item/MM2_1988__61_4_155316/ %F MM2_1988__61_4_155316