@article{1103038067,
author = {Hewitt, Edwin and Zuckerman, H. S.},
title = {The multiplicative semigroup of integers modulo $m$.},
journal = {Pacific J. Math.},
volume = {10},
number = {4},
year = {1960},
pages = { 1291-1308},
language = {en},
url = {http://dml.mathdoc.fr/item/1103038067}
}
Hewitt, Edwin; Zuckerman, H. S. The multiplicative semigroup of integers modulo $m$.. Pacific J. Math., Tome 10 (1960) no. 4, pp. 1291-1308. http://gdmltest.u-ga.fr/item/1103038067/