@article{CMJ_2008_58_2_a1,
     author = {Descal\c{c}o, L. and Ru\v{s}kuc, N.},
     title = {Properties of the subsemigroups of the bicyclic monoid},
     journal = {Czechoslovak Mathematical Journal},
     pages = {311--330},
     year = {2008},
     volume = {58},
     number = {2},
     mrnumber = {2411092},
     zbl = {1166.20052},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMJ_2008_58_2_a1/}
}