@article{SF_1993__47_2_135270,
     author = {W. Li},
     title = {Green's relations on the strong endomorphism monoid of a graph.},
     journal = {Semigroup forum},
     pages = {209--214},
     publisher = {mathdoc},
     volume = {47},
     number = {2},
     year = {1993},
     zbl = {0791.20077},
     url = {http://geodesic.mathdoc.fr/item/SF_1993__47_2_135270/}
}