@article{MS2_1967__20_165984,
     author = {N. Oler},
     title = {On {Subgroups} of the {First} {Kind.}},
     journal = {Mathematica Scandinavica},
     pages = {91--92},
     publisher = {mathdoc},
     volume = {20},
     year = {1967},
     zbl = {0189.02703},
     url = {http://geodesic.mathdoc.fr/item/MS2_1967__20_165984/}
}