@article{SF_1977__15_134239,
     author = {V. Schneider},
     title = {Semigroups and the n-sphere.},
     journal = {Semigroup forum},
     pages = {93--94},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0369.22005},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__15_134239/}
}