@article{10_4153_CMB_1975_103_x,
     author = {Porter, Jack R.},
     title = {Extension {Function} and {Subcategories} of {Haus}},
     journal = {Canadian mathematical bulletin},
     pages = {587--590},
     year = {1975},
     volume = {18},
     number = {4},
     doi = {10.4153/CMB-1975-103-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1975-103-x/}
}