Boundary control theory for hyperbolic and parabolic partial differential equations with constant coefficients

Littman, Walter

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Volume 5 (1978) p. 567-580

“Farfield” behavior of solutions to partial differential equations : asymptotic expansions and maximal rates of decay along a ray

Arena, Orazio; Littman, Walter

Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche, Volume 26 (1972) p. 807-827