@article{MOMA_1960__64_177100,
     author = {Eckford Cohen},
     title = {The {Average} {Order} of {Certain} {Types} of {Arithmetical} {Functions:} {Generalized} k-free {Numbers} and {Totient} {Points.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {251--262},
     publisher = {mathdoc},
     volume = {64},
     year = {1960},
     zbl = {0116.27103},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1960__64_177100/}
}