@article{1183425068, author = {Bell, E. T.}, title = {On the number of representations of $2n$ as a sum of $2r$ squares}, journal = {Bull. Amer. Math. Soc.}, volume = {26}, number = {3}, year = {1919}, pages = { 19-25}, language = {en}, url = {http://dml.mathdoc.fr/item/1183425068} }
Bell, E. T. On the number of representations of $2n$ as a sum of $2r$ squares. Bull. Amer. Math. Soc., Tome 26 (1919) no. 3, pp. 19-25. http://gdmltest.u-ga.fr/item/1183425068/