@article{SF_1974__6_133987,
     author = {G.L. White},
     title = {The dual ordinal of a bisimple inverse semigroup.},
     journal = {Semigroup forum},
     pages = {295--297},
     year = {1974},
     volume = {6},
     zbl = {0267.20055},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__6_133987/}
}