@article{10_4153_CMB_1978_034_3,
     author = {Penna, Michael A.},
     title = {On a {Theorem} of {Sullivan}},
     journal = {Canadian mathematical bulletin},
     pages = {201--206},
     year = {1978},
     volume = {21},
     number = {2},
     doi = {10.4153/CMB-1978-034-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-034-3/}
}