@article{SF_1984__29_134684,
     author = {F. Otto},
     title = {Conjugacy in monoids.},
     journal = {Semigroup forum},
     pages = {223--240},
     publisher = {mathdoc},
     volume = {29},
     year = {1984},
     zbl = {0551.20044},
     url = {http://geodesic.mathdoc.fr/item/SF_1984__29_134684/}
}