@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/