@article{PORMA_1974__33_4_115237,
     author = {Morgado, Jos\'e},
     title = {A property of the {Euler} $\varphi $-function concerning the integers which are regular modulo n},
     journal = {Portugaliae mathematica},
     pages = {185--191},
     publisher = {mathdoc},
     volume = {33},
     number = {4},
     year = {1974},
     mrnumber = {0419336},
     zbl = {0302.10003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1974__33_4_115237/}
}