@article{JMPA_1929_9_8__145_0,
     author = {Humbert, Pierre},
     title = {Sur une g\'en\'eralisation de l'\'equation de {Laplace}},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {145--159},
     publisher = {Gauthier-Villars},
     volume = {9e s{\'e}rie, 8},
     year = {1929},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1929_9_8__145_0/}
}