@article{SF_1990__40_1_135023,
     author = {R. McFadden and J.M. Howie},
     title = {Ideals are greater on the left.},
     journal = {Semigroup forum},
     pages = {247--248},
     year = {1990},
     volume = {40},
     number = {1},
     zbl = {0692.20054},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__40_1_135023/}
}