@article{AM2_1981__22_136883,
     author = {George M. Bergman},
     title = {Hyperidentities of groups and semigroups. {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {315--317},
     publisher = {mathdoc},
     volume = {22},
     year = {1981},
     zbl = {0453.08003},
     url = {http://geodesic.mathdoc.fr/item/AM2_1981__22_136883/}
}