@article{SF_1972__5_133932,
     author = {Y. Chae},
     title = {Multi-mobs.},
     journal = {Semigroup forum},
     pages = {154--159},
     publisher = {mathdoc},
     volume = {5},
     year = {1972},
     zbl = {0267.22002},
     url = {http://geodesic.mathdoc.fr/item/SF_1972__5_133932/}
}