@article{ADM_2011_12_1_a3,
     author = {J. Meksawang and S. Panma and U. Knauer},
     title = {Characterization of finite simple semigroup digraphs},
     journal = {Algebra and discrete mathematics},
     pages = {53--68},
     publisher = {mathdoc},
     volume = {12},
     number = {1},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2011_12_1_a3/}
}