@article{JMPA_1912_6_8__1_0,
     author = {Duhem, P.},
     title = {Sur le principe {d'Optique} g\'eom\'etrique \'enonc\'e par {Fermat}},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {1--58},
     publisher = {Gauthier-Villars},
     volume = {6e s{\'e}rie, 8},
     year = {1912},
     language = {fr},
     url = {http://archive.numdam.org/item/JMPA_1912_6_8__1_0/}
}