@article{10_4153_CMB_1973_052_4,
     author = {Rishel, Thomas W.},
     title = {Images {Of} {Class-} {Spaces}},
     journal = {Canadian mathematical bulletin},
     pages = {323--328},
     year = {1973},
     volume = {16},
     number = {3},
     doi = {10.4153/CMB-1973-052-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1973-052-4/}
}