@article{02100248,
title = {Lines of curvature, ridges and conformal invariants of hypersurfaces.},
journal = {Beitr\"age zur Algebra und Geometrie},
volume = {45},
year = {2004},
pages = {615-635},
zbl = {1093.53018},
language = {en},
url = {http://dml.mathdoc.fr/item/02100248}
}
Romero-Fuster, M.C.; Sanabria-Codesal, E. Lines of curvature, ridges and conformal invariants of hypersurfaces.. Beiträge zur Algebra und Geometrie, Tome 45 (2004) pp. 615-635. http://gdmltest.u-ga.fr/item/02100248/