@article{SF_1980__19_134380,
     author = {K.P. Shum and S.Y. Kwan},
     title = {Lattices of order ideals on ordered semigroups.},
     journal = {Semigroup forum},
     pages = {151--176},
     publisher = {mathdoc},
     volume = {19},
     year = {1980},
     zbl = {0438.06010},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__19_134380/}
}