@article{1183523033,
author = {Lewy, Hans},
title = {On the reflection laws of second order differential equations in two independent variables},
journal = {Bull. Amer. Math. Soc.},
volume = {65},
number = {6},
year = {1959},
pages = { 37-58},
language = {en},
url = {http://dml.mathdoc.fr/item/1183523033}
}
Lewy, Hans. On the reflection laws of second order differential equations in two independent variables. Bull. Amer. Math. Soc., Tome 65 (1959) no. 6, pp. 37-58. http://gdmltest.u-ga.fr/item/1183523033/