Given "n" and "m", one can reverse this theoretical operation by drawing the vector w on the graphene lattice, cutting a strip of the latter along lines perpendicular to w through its endpoints "A1" and "A2", and rolling the strip into a cylinder so as to bring those two points together. If this construction is applied to a pair ("k",0), the result is a zigzag nanotube, with closed zigzag paths of 2"k" atoms. If it is applied to a pair ("k","k"), one obtains an armchair tube, with closed armchair paths of 4"k" atoms.