%0 Journal Article %A Tuomas Sorvali %T On the dilatation of isomorphisms between covering groups %J Annales Fennici Mathematici %D 1973 %V 521-560 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1973.551/ %R 10.5186/aasfm.1973.551 %G en %F AFM_1973_521-560_a9