@article{10_4153_CMB_1991_082_1,
     author = {Pakula, Lewis and Schwartzman, Sol},
     title = {Independence for {Sets} of {Topological} {Spheres}},
     journal = {Canadian mathematical bulletin},
     pages = {520--524},
     year = {1991},
     volume = {34},
     number = {4},
     doi = {10.4153/CMB-1991-082-1},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1991-082-1/}
}