@article{GDZPPN002171899,
title = {On binary quadratic forms expressable as a sum of three linear squares with integer coefficients.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {166},
year = {1932},
pages = {12-19},
zbl = {0003.19302},
url = {http://dml.mathdoc.fr/item/GDZPPN002171899}
}
Mordell, L.J. On binary quadratic forms expressable as a sum of three linear squares with integer coefficients.. Journal für die reine und angewandte Mathematik, Tome 166 (1932) pp. 12-19. http://gdmltest.u-ga.fr/item/GDZPPN002171899/