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@article{PORMA_1962__21_4_114894, author = {Morgado, Jos\'e}, title = {Unitary analogue of the {Nagell} totient function}, journal = {Portugaliae mathematica}, pages = {221--232}, publisher = {mathdoc}, volume = {21}, number = {4}, year = {1962}, mrnumber = {0146128}, zbl = {0111.25202}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1962__21_4_114894/} }
Morgado, José. Unitary analogue of the Nagell totient function. Portugaliae mathematica, Tome 21 (1962) no. 4, pp. 221-232. http://geodesic.mathdoc.fr/item/PORMA_1962__21_4_114894/