%0 Journal Article %A Kenneth Williams %A Kenneth Hardy %T A congruence for the index of a unit of a real abelian number field %J Acta Arithmetica %D 1985 %P 57-72 %V 46 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/aa-46-1-57-72/ %R 10.4064/aa-46-1-57-72 %G en %F 10_4064_aa_46_1_57_72