@article{10_4153_CMB_1981_037_1,
     author = {Hoffmann, Rudolf-E.},
     title = {Essential {Extensions} of {T1-Spaces}},
     journal = {Canadian mathematical bulletin},
     pages = {237--240},
     year = {1981},
     volume = {24},
     number = {2},
     doi = {10.4153/CMB-1981-037-1},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1981-037-1/}
}