Singular conformally invariant trilinear forms and generalized Rankin   Cohen operators
  The most singular residues of the standard meromorphic family of trilinear conformally invariant forms on $\mathcal C^\infty_c(\mathbb R^d)$ are computed. Their expression involves covariant bidifferential operators (generalized Rankin Cohen operators), for which new formul\ae \ are obtained. The main tool is a Bernstein-Sato identity for the kernel of the forms. 
Clerc Jean-Louis and Beckmann Ralf
math.RT