@article{TSG_1991-1992__10__9_0,
     author = {Sotomayor, Jorge},
     title = {Lines of curvature and umbilic points on surfaces},
     journal = {S\'eminaire de th\'eorie spectrale et g\'eom\'etrie},
     pages = {9--12},
     publisher = {Institut Fourier},
     address = {Grenoble},
     volume = {10},
     year = {1991-1992},
     mrnumber = {1715907},
     language = {en},
     url = {http://www.numdam.org/item/TSG_1991-1992__10__9_0/}
}