@incollection{AST_1983__98-99__195_0,
     author = {Sotomayor, J. and Gutierrez, C.},
     title = {Structurally stable configurations of lines of principal curvature},
     booktitle = {Bifurcation, th\'eorie ergodique et applications - 22-26 juin 1981},
     series = {Ast\'erisque},
     pages = {195--215},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {98-99},
     year = {1982},
     mrnumber = {724448},
     zbl = {0521.53003},
     language = {en},
     url = {http://www.numdam.org/item/AST_1983__98-99__195_0/}
}