@article{1077379466,
author = {Stevens, Harlan},
title = {Generalizations of the Euler
$\varphi$ -function},
journal = {Duke Math. J.},
volume = {38},
number = {1},
year = {1971},
pages = { 181-186},
language = {en},
url = {http://dml.mathdoc.fr/item/1077379466}
}
Stevens, Harlan. Generalizations of the Euler $\varphi$ -function. Duke Math. J., Volume 38 (1971) no. 1, pp. 181-186. http://gdmltest.u-ga.fr/item/1077379466/