@article{ELMA_1981__36_141258,
     author = {Aleksandr Grytczuk},
     title = {An identity involving {Ramanujan's} sum.},
     journal = {Elemente der Mathematik},
     pages = {16--24},
     publisher = {mathdoc},
     volume = {36},
     year = {1981},
     zbl = {0447.10009},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1981__36_141258/}
}