▎ 摘　　要

Explicit expressions of the band spectrum near the neutrality point are derived for armchair and zigzag graphene ribbons and carbon tubes. Several spectral features, which were previously observed only in numerical calculations, are given an adequate analytic description in terms of elementary functions. The obtained dispersion relations are used for a comparison of conductance ladders of graphene-based wires; these relations are also beneficial for many other applications.