@article{JMPA_1939_9_18__1_0,
     author = {Vessiot, E.},
     title = {Sur les \'equations aux d\'eriv\'ees partielles du second ordre, $\mathrm{F} \left(x, y, z, p, q, r, s, t\right) = o$, int\'egrables par la m\'ethode de {Darboux}},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {1--61},
     publisher = {Gauthier-Villars},
     volume = {9e s{\'e}rie, 18},
     year = {1939},
     zbl = {0020.30104},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1939_9_18__1_0/}
}