@article{1178240740,
author = {Nakamura, Gen and Sasai, Takao},
title = {The singularities of the solutions of the Cauchy problem for second order equations in case the initial manifold includes characteristic points},
journal = {Tohoku Math. J. (2)},
volume = {28},
number = {4},
year = {1976},
pages = { 523-539},
language = {en},
url = {http://dml.mathdoc.fr/item/1178240740}
}
Nakamura, Gen; Sasai, Takao. The singularities of the solutions of the Cauchy problem for second order equations in case the initial manifold includes characteristic points. Tohoku Math. J. (2), Tome 28 (1976) no. 4, pp. 523-539. http://gdmltest.u-ga.fr/item/1178240740/