Interaction between concentric tubes in DWCNTs R. Pfeiffer, Ch. Kramberger, F. Simon, H. Kuzmany, V. N. Popov and H. Kataura Eur. Phys. J. B, 42 3 (2004) 345-350 Published online: 23 December 2004 DOI: 10.1140/epjb/e2004-00389-0