@article{10_4153_CJM_1968_141_2,
     author = {Alltop, W. O.},
     title = {Free {Planes} and {Collineations}},
     journal = {Canadian journal of mathematics},
     pages = {1397--1411},
     year = {1968},
     volume = {20},
     number = {1},
     doi = {10.4153/CJM-1968-141-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-141-2/}
}