@article{GDZPPN002311275, title = {Stability of Caustics.}, journal = {Mathematische Annalen}, volume = {217}, year = {1975}, pages = {43-50}, zbl = {0293.58008}, url = {http://dml.mathdoc.fr/item/GDZPPN002311275} }
Wassermann, Gordon. Stability of Caustics.. Mathematische Annalen, Tome 217 (1975) pp. 43-50. http://gdmltest.u-ga.fr/item/GDZPPN002311275/