Global existence and asymptotic behavior of solutions for the Klein-Gordon equations with quadratic nonlinearity in two space dimensions. Tohru Ozawa; Y. Tsutsumi; K. Tsutaya — 1996 Mathematische Zeitschrift
Normal form and global solutions for the Klein-Gordon-Zakharov equations T. Ozawa; K. Tsutaya; Y. Tsutsumi — 1995 Annales de l'I.H.P. Analyse non linéaire