@article{PORMA_1973__32_3_115202,
     author = {Shader, Leslie E.},
     title = {Closed form expressions for several {Ramanujan} sums},
     journal = {Portugaliae mathematica},
     pages = {147--153},
     publisher = {mathdoc},
     volume = {32},
     number = {3},
     year = {1973},
     mrnumber = {0314805},
     zbl = {0256.10003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1973__32_3_115202/}
}