@article{SF_1991__43_3_135113,
     author = {A. Foster},
     title = {Another semigroup of complexity n-1.},
     journal = {Semigroup forum},
     pages = {257--259},
     publisher = {mathdoc},
     volume = {43},
     number = {3},
     year = {1991},
     zbl = {0737.20028},
     url = {http://geodesic.mathdoc.fr/item/SF_1991__43_3_135113/}
}