@Article{DT214,
  title = {Helicity in Ropes of Chiral Nanotubes:
           Calculations and Observation},
  author = {Teich, David and Seifert, Gotthard and Iijima, Sumio
            and Tom\'anek, David},
  journal = {Phys. Rev. Lett.},
  volume = {108},
  issue = {23},
  pages = {235501},
  numpages = {5},
  year = {2012},
  month = {Jun},
  doi = {10.1103/PhysRevLett.108.235501},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.108.235501},
  publisher = {American Physical Society}
}