@article{JRAM_1981__323_152343,
     author = {W. Narkiewicz},
     title = {Euler's function and the sum of divisors.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {200--212},
     publisher = {mathdoc},
     volume = {323},
     year = {1981},
     zbl = {0447.10050},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1981__323_152343/}
}