Only ellipsoids have caustics.
Gruber, Peter M.
Mathematische Annalen, Tome 302 (1995), p. 185-194 / Harvested from Göttinger Digitalisierungszentrum
Access to full text
Publié le : 1995-01-01
EUDML-ID : urn:eudml:doc:165364 
@article{GDZPPN002341069,
     title = {Only ellipsoids have caustics.},
     journal = {Mathematische Annalen},
     volume = {302},
     year = {1995},
     pages = {185-194},
     zbl = {0847.34052},
     url = {http://dml.mathdoc.fr/item/GDZPPN002341069}
}

Gruber, Peter M. Only ellipsoids have caustics.. Mathematische Annalen, Tome 302 (1995) pp. 185-194. http://gdmltest.u-ga.fr/item/GDZPPN002341069/