@article{JMPA_1864_2_9__17_0,
     author = {Liouville, J.},
     title = {Sur la forme $x^2+5\left(y^2+z^2+t^2\right)$},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {17--22},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 9},
     year = {1864},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1864_2_9__17_0/}
}