Stabilizing and commuting cochains

As it is well known in K-theory, stabilization of matrices enables them to commute “up to homotopy”. The purpose of this short paper is to describe an analogous philosophy for cochains on a space. It is in fact a direct application of a paper of Henri Cartan [1], together with a new idea of stabilization for cochains, similar to matrices. The application below may be also deduced from a paper of J. Halperin and J. Stasheff [2] by a quite different method. This paper is part of a joint project with P. Baum about the cohomology of homogeneous spaces. Since it has some independent interest, it might be useful to present it on its own right.