@article{SF_1978__16_134287,
     author = {A.H. Clifford},
     title = {Remarks on 0-minimal quasi-ideals in semigroups.},
     journal = {Semigroup forum},
     pages = {183--196},
     year = {1978},
     volume = {16},
     zbl = {0394.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1978__16_134287/}
}