@article{JMPA_1847_1_12__343_0,
     author = {Bertrand, J.},
     title = {Note sur la th\'eorie des normales \`a une m\^eme surface},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {343--346},
     publisher = {Gauthier-Villars},
     volume = {1e s{\'e}rie, 12},
     year = {1847},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1847_1_12__343_0/}
}