@article{GDZPPN002472902,
title = {The Average Order of Certain Types of Arithmetical Functions: Generalized k-free Numbers and Totient Points.},
journal = {Monatshefte f\"ur Mathematik},
volume = {64},
year = {1960},
pages = {251-262},
zbl = {0116.27103},
url = {http://dml.mathdoc.fr/item/GDZPPN002472902}
}
Cohen, Eckford. The Average Order of Certain Types of Arithmetical Functions: Generalized k-free Numbers and Totient Points.. Monatshefte für Mathematik, Tome 64 (1960) pp. 251-262. http://gdmltest.u-ga.fr/item/GDZPPN002472902/