@article{MS2_1961__9_165764,
     author = {Edward S. O'Keefe},
     title = {Verification of a {Conjecture} of {Th.} {Skolem.}},
     journal = {Mathematica Scandinavica},
     pages = {80--82},
     publisher = {mathdoc},
     volume = {9},
     year = {1961},
     zbl = {0105.25003},
     url = {http://geodesic.mathdoc.fr/item/MS2_1961__9_165764/}
}