In the first part of this paper, we give a new analytical proof theorem C. Sabbah on integrable deformations meromorphic connections $\mathbb P^1$ with coalescing irregular singularities Poincar\'e rank 1, and generalizing previous result B. Malgrange. second as an application, prove that any semisimple formal Frobenius manifold (over C$), unit Euler field, is completion analytic pointed germ D...