@article{10_4153_CJM_1967_033_4,
     author = {Heppes, Alad\'ar},
     title = {On the {Number} of {Spheres} {Which} can {Hide} a {Given} {Sphere}},
     journal = {Canadian journal of mathematics},
     pages = {413--418},
     year = {1967},
     volume = {19},
     number = {1},
     doi = {10.4153/CJM-1967-033-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1967-033-4/}
}