@article{JMPA_1865_2_10__14_0,
     author = {Liouville, J.},
     title = {Sur la forme $x^2+y^2+9z^2+9t^2$},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {14--20},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 10},
     year = {1865},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1865_2_10__14_0/}
}