@article{CTGDC_1988__29_2_157_0,
     author = {Johnstone, P. T.},
     title = {A simple proof that localic subgroups are closed},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     pages = {157--161},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {29},
     number = {2},
     year = {1988},
     mrnumber = {943899},
     zbl = {0648.18007},
     language = {en},
     url = {http://www.numdam.org/item/CTGDC_1988__29_2_157_0/}
}