@article{10_21136_CMJ_1974_101274,
     author = {Hoo, Cheong Seng and Shum, Kar-Ping},
     title = {On compact $N$-semigroups},
     journal = {Czechoslovak Mathematical Journal},
     pages = {552--562},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {1974},
     doi = {10.21136/CMJ.1974.101274},
     mrnumber = {0374321},
     zbl = {0332.22003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1974.101274/}
}