A link between C ∞ and analytic solvability for P.D.E. with constant coefficients Giuseppe Zampieri (1980) Rendiconti del Seminario Matematico della Università di Padova
A sufficient condition for existence of real analytic solutions of P.D.E. with constant coefficients, in open sets of ℝ 2 Giuseppe Zampieri (1980) Rendiconti del Seminario Matematico della Università di Padova