@article{1256059574,
author = {Wohlfahrt, Klaus},
title = {An extension of F. Klein's level concept},
journal = {Illinois J. Math.},
volume = {8},
number = {4},
year = {1964},
pages = { 529-535},
language = {en},
url = {http://dml.mathdoc.fr/item/1256059574}
}
Wohlfahrt, Klaus. An extension of F. Klein's level concept. Illinois J. Math., Tome 8 (1964) no. 4, pp. 529-535. http://gdmltest.u-ga.fr/item/1256059574/