$K_{1,2,2,2}$ has no $n$-fold planar cover graph for $n<14$

Dickson Y. B. Annor, Yuri Nikolayevsky, Michael S. Payne

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. Fe…