00291nam a2200109Ia 4500100001700000110002800017245005200045260002400097300000900121490004600130490000500176  aZarati, Said  aUniversite de Paris-Sud  aDefaut de stabilite d'operations cohomologiques  aOrsay, Francec1978  a60p.  aPublications Mathematiques D'Orsay; 78-07  a