\(K_{1,2,2,2}\) has no n-fold planar cover for \(n<14\)
摘要
S. Negami conjectured in 1988 that a connected graph has a finite planar cover if and only if it embeds in the projective plane. It follows from the works of D. Archdeacon, M. Fellows, P. Hliněný, and S. Negami that this conjecture is true if the graph