@article{MZ_1970__115_171342,
     author = {Ronald D. Bercov and Charles R. Hobby},
     title = {Permutation {Groups} on {Unordered} {Sets.}},
     journal = {Mathematische Zeitschrift},
     pages = {165--168},
     publisher = {mathdoc},
     volume = {115},
     year = {1970},
     zbl = {0186.32301},
     url = {http://geodesic.mathdoc.fr/item/MZ_1970__115_171342/}
}