@article{1181072908,
author = {Hofmann, Karl H. and Strambach, Karl},
title = {Idempotent Multiplications on Surfaces and Aspherical Spaces},
journal = {Rocky Mountain J. Math.},
volume = {21},
number = {4},
year = {1991},
pages = { 1279-1310},
language = {en},
url = {http://dml.mathdoc.fr/item/1181072908}
}
Hofmann, Karl H.; Strambach, Karl. Idempotent Multiplications on Surfaces and Aspherical Spaces. Rocky Mountain J. Math., Tome 21 (1991) no. 4, pp. 1279-1310. http://gdmltest.u-ga.fr/item/1181072908/