Y.F. Suprunenko, E.V. Gorbar, S.G. Sharapov, and V.M. Loktev, Effect of next-to-nearest neighbor hopping on electronic properties of graphene: Graphene and graphite multilayers, Low Temp. Phys. 34, (2008) [Fiz. Nizk. Temp. 34, 1033-1039, (2008)] DOI: https://doi.org/10.1063/1.2981394.