@article{JMPA_1863_2_8__120_0,
     author = {Liouville, J.},
     title = {Sur la forme $x^2+y^2+z^2+zt^2+t^2$},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {120--123},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 8},
     year = {1863},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1863_2_8__120_0/}
}