  An A_\infty-bialgebra is a DGM H equipped with structurally compatible
operations {\omega^{j,i} : H^{\otimes i} --> H^{\otimes j}} such that
(H,\omega^{1,i}) is an A_\infty-algebra and (H,\omega^{j,1}) is an
A_\infty-coalgebra. Structural compatibility is controlled by the biderivative
operator Bd, defined in terms of two kinds of cup products on certain cochain
algebras of pemutahedra over the universal PROP U = End(TH).
