@article{MZ_1967__97_170703,
     author = {T.G. Ostrom},
     title = {Closure with {Respect} to {Subplanes.}},
     journal = {Mathematische Zeitschrift},
     pages = {57--65},
     year = {1967},
     volume = {97},
     zbl = {0144.19503},
     url = {http://geodesic.mathdoc.fr/item/MZ_1967__97_170703/}
}