@article{ASENS_1865_1_2__55_0,
     author = {Darboux, Gaston},
     title = {Recherches sur les surfaces orthogonales},
     journal = {Annales scientifiques de l'\'Ecole Normale Sup\'erieure},
     publisher = {Elsevier},
     volume = {1e s{\'e}rie, 2},
     year = {1865},
     pages = {55-69},
     doi = {10.24033/asens.12},
     mrnumber = {1508514},
     language = {fr},
     url = {http://www.numdam.org/item/ASENS_1865_1_2__55_0}
}

Darboux, G. Recherches sur les surfaces orthogonales. Annales scientifiques de l'École Normale Supérieure, Serie 1, Volume 2 (1865) , pp. 55-69. doi : 10.24033/asens.12. http://www.numdam.org/item/ASENS_1865_1_2__55_0/