1. The closest packing of equal circles on a sphere;Clare,1986
2. Sphere Packings, Lattices and Groups;Conway,1993
3. Unsolved Problems in Geometry;Croft,1991
4. Lagerungen in der Ebene, auf der Kugel und im Raum;Fejes Tóth,1972
5. Packing of 14, 16, 17 and 20 circles in a circle;Goldberg;Math. Mag.,1971