@article{SF_1993__46_1_135203,
     author = {K.P. Shum and M.W. Chan},
     title = {Homomorphisms of implicative semigroups.},
     journal = {Semigroup forum},
     pages = {7--15},
     publisher = {mathdoc},
     volume = {46},
     number = {1},
     year = {1993},
     zbl = {0776.06012},
     url = {http://geodesic.mathdoc.fr/item/SF_1993__46_1_135203/}
}