@article{SF_1994__49_2_135351,
     author = {P.M. Higgins},
     title = {The {Mitsch} order on a semigroup.},
     journal = {Semigroup forum},
     pages = {261--266},
     publisher = {mathdoc},
     volume = {49},
     number = {2},
     year = {1994},
     zbl = {0809.20052},
     url = {http://geodesic.mathdoc.fr/item/SF_1994__49_2_135351/}
}