Altunbulak, A. F.Green, D. J.2015-07-282015-07-282009-120022-4049http://hdl.handle.net/11693/13467For an odd prime p the cohomology ring of an elementary abelian p-group is polynomial tensor exterior. We show that the ideal of essential classes is the Steenrod closure of the class generating the top exterior power. As a module over the polynomial algebra, the essential ideal is free on the set of Mùi invariants. © 2009 Elsevier B.V. All rights reserved.EnglishInvariantsArticle10.1016/j.jpaa.2009.04.0161873-1376