A.L. Miettinen, M.S. Nevius, W. Ko, M. Kolmer, A.-P Li, M.N. Nair, A. Taleb-Ibrahimi, B. Kierren, L. Moreau, E.H. Conrad and A. Tejeda. Edge states and ballistic transport in zig-zag graphene ribbons: the role of SiC polytypes, Phys. Rev. B., 2019, 100, 045425.