Let $\Pi$ denote the McMullen polytope algebra (over the field of rationals $\mathbb{Q}$) generated by convex polytopes with rational vertices in $\mathbb{R}^n$.
For a simple polytope $P$ let us denote by $\Pi(P)$ the subalgebra of $\Pi$ generated by Minkowski summands of $P$. ($Q$ is a Minkowski summand of $P$ if $P=Q+Q'$ for another convex polytope $Q'$.
As far as I heard the algebra $\Pi(P)$ is isomorphic to the cohomology algebra of the toric variety corresponding to $P$.
Question. I would like to have a reference to this statement and a construction of the isomorphism. (The case of a smooth toric variety would be sufficient for me for the moment.)