“…In view of existence results such as the theorem of Cauchy-Kovalevsky [5, Theorem 9.4.5], or the propagation of singularities of solutions to the analytic Cauchy problem [24], this question is central in the à priori estimation of the domain of analytic continuability of solutions across the boundary. This, in turn, is applicable, e.g., in the stability and convergence analysis of 'interior source methods', which is a family of promising numerical methods for direct and inverse elliptic boundary problems [2,3,8,9,10,11].…”