The structure of multi-wall carbon nanotubes: AA' stacked graphene   helices
  The structure of multi-wall carbon nanotubes has been attributed previously to disordered stacking of the graphene planes. 
Jae-Kap Lee, Sohyung Lee, Yong-Il Kim, Jin-Gyu Kim, Kyung-Il Lee,   Jae-Pyoung Ahn, Bong-Ki Min, Chung-Jong Yu, Keun Hwa Cha...
cond-mat.mtrl-sci cond-mat.mes-hall