@article{1183425209,
author = {Bell, E. T.},
title = {Definition and illustrations of new arithmetical group invariants},
journal = {Bull. Amer. Math. Soc.},
volume = {27},
number = {3},
year = {1920},
pages = { 211-223},
language = {en},
url = {http://dml.mathdoc.fr/item/1183425209}
}
Bell, E. T. Definition and illustrations of new arithmetical group invariants. Bull. Amer. Math. Soc., Tome 27 (1920) no. 3, pp. 211-223. http://gdmltest.u-ga.fr/item/1183425209/