@article{1183425280,
author = {Bell, E. T.},
title = {The equation $ds^2 = dx^2 + dy^2 + dz^2$},
journal = {Bull. Amer. Math. Soc.},
volume = {27},
number = {3},
year = {1920},
pages = { 312-318},
language = {en},
url = {http://dml.mathdoc.fr/item/1183425280}
}
Bell, E. T. The equation $ds^2 = dx^2 + dy^2 + dz^2$. Bull. Amer. Math. Soc., Tome 27 (1920) no. 3, pp. 312-318. http://gdmltest.u-ga.fr/item/1183425280/