Using hyperbolic form convolution with doubly isometry-invariant kernels, the explicit expression of the inverse of the de Rham laplacian ∆ acting on m-forms in the Poincaré space H is found. Also, by means of some estimates for hyperbolic singular integrals, L-estimates for the Riesz transforms ∇i∆−1, i ≤ 2, in a range of p depending on m,n are obtained. Finally, using these, it is shown that ...