00283nam a2200109Ia 4500100001800000110002400018245004600042260002400088300001000112490004600122490000500168  aDitters, Bert  aUniversite Paris XI  aGroupes formelsbCours 3e cycle 1973-1974  aOrsay, Francec1975  a108p.  aPublications Mathematiques D'Orsay; 75-42  a