Y Okada   H Yamane   
JOURNAL DE MATHEMATIQUES PURES ET APPLIQUEES 75(6) 559-567 1996年 [査読有り]
Garding-Kotake-Leray studied a characteristic Cauchy problem Pu = v epsilon O with zero Cauchy data on a hypersurface S. They showed that u can be ramified of order q around another hypersurface K, which has a contact of order q - 1 with S along t...