@article{JMPA_1860_2_5__147_0,
     author = {Liouville, J.},
     title = {Sur la forme $x^2+y^2+3\left(z^2+t^2\right)$},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {147--152},
     publisher = {Gauthier-Villars},
     volume = {2e s{\'e}rie, 5},
     year = {1860},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1860_2_5__147_0/}
}