@article{1183498917, author = {Bell, E. T.}, title = {The form $wx + xy + yz + zu$}, journal = {Bull. Amer. Math. Soc.}, volume = {42}, number = {12}, year = {1936}, pages = { 377-380}, language = {en}, url = {http://dml.mathdoc.fr/item/1183498917} }
Bell, E. T. The form $wx + xy + yz + zu$. Bull. Amer. Math. Soc., Tome 42 (1936) no. 12, pp. 377-380. http://gdmltest.u-ga.fr/item/1183498917/