@article{GDZPPN002080214,
title = {An identity involving Ramanujan's sum.},
journal = {Elemente der Mathematik},
volume = {36},
year = {1981},
pages = {16-24},
zbl = {0447.10009},
url = {http://dml.mathdoc.fr/item/GDZPPN002080214}
}
Grytczuk, Aleksandr. An identity involving Ramanujan's sum.. Elemente der Mathematik, Tome 36 (1981) pp. 16-24. http://gdmltest.u-ga.fr/item/GDZPPN002080214/