@article{MASLO_1966_16_3_a0,
     author = {Wallace, Alexander Doniphan},
     title = {Problems on {Periodicity} - {Functions} and {Semigroups}},
     journal = {Mathematica slovaca},
     pages = {209--212},
     year = {1966},
     volume = {16},
     number = {3},
     mrnumber = {0212774},
     zbl = {0152.21501},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1966_16_3_a0/}
}