Smoothness and analycity for solutions of first order systems of partial differential equations on nilpotent Lie groups.
Page 1
Lawrence. Corwin, B. Helffer (1985)
Inventiones mathematicae
M. I. Višik, A. V. Foursikov (1977)
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze
J. Szarski (1975)
Annales Polonici Mathematici
Page 1