In this paper, we introduce Adem-Cartan operads and prove that the cohomology
of any algebra over such an operad is an unstable level algebra over the
extended Steenrod algebra. Moreover we prove that this cohomology is endowed
with secondary cohomological operations.Comment: 26 pages, LaTeX. Replacemnet of "operadic description of Steenrod
  operations". It is a new approach (more conceptual) of the results of the
  previous pape

Chataur, D.

Livernet, M.