@article{JMPA_1864_2_9__421_0,
     author = {Liouville, J.},
     title = {Sur la forme $x^2+2\left(y^2+z^2+t^2+u^2\right)+4\nu^2$},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {421--424},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 9},
     year = {1864},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1864_2_9__421_0/}
}