@article{SF_1987__36_134896,
     author = {J.W. Hogan},
     title = {Hausdorff  topologies on the a-bicyclic semigroup.},
     journal = {Semigroup forum},
     pages = {189--210},
     publisher = {mathdoc},
     volume = {36},
     year = {1987},
     zbl = {0626.22002},
     url = {http://geodesic.mathdoc.fr/item/SF_1987__36_134896/}
}