@article{SF_1974__9_134055,
     author = {B. Madison and Lawson J.},
     title = {Quotients of k-semigroups.},
     journal = {Semigroup forum},
     pages = {1--18},
     publisher = {mathdoc},
     volume = {9},
     year = {1974},
     zbl = {0288.22006},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__9_134055/}
}