@article{01787968,
title = {Extended affine root systems.},
journal = {Journal of Lie Theory},
volume = {12},
year = {2002},
pages = {515-527},
zbl = {1014.17020},
language = {en},
url = {http://dml.mathdoc.fr/item/01787968}
}
Azam, Saeid. Extended affine root systems.. Journal of Lie Theory, Tome 12 (2002) pp. 515-527. http://gdmltest.u-ga.fr/item/01787968/