@article{JMPA_1873_2_18__236_0,
     author = {Darboux, G.},
     title = {Sur l'int\'egration de l'\'equation $dx^2+dy^2=ds^2$ et de quelques \'equations analogues},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {236--240},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 18},
     year = {1873},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1873_2_18__236_0/}
}