Symmetry, phonons and rigid-layers modes in commensurate double wall carbon nanotubesE. Dobardžić, I. Milošević, T. Vuković, B. Nikolić and M. DamnjanovićEur. Phys. J. B, 34 4 (2003) 409-413DOI: https://doi.org/10.1140/epjb/e2003-00238-8