@article{10_21136_CMJ_1969_100879,
     author = {Kim, Jin Bai},
     title = {Mutants in semigroups},
     journal = {Czechoslovak Mathematical Journal},
     pages = {86--90},
     publisher = {mathdoc},
     volume = {19},
     number = {1},
     year = {1969},
     doi = {10.21136/CMJ.1969.100879},
     mrnumber = {0238973},
     zbl = {0175.01704},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1969.100879/}
}