  Electronic properties of bilayer and multilayer graphene have generally been
interpreted in terms of AB or Bernal stacking. However, it is known that many
types of stacking defects can occur in natural and synthetic graphite; rotation
of the top layer is often seen in scanning tunneling microscopy (STM) studies
of graphite. In this paper we consider a graphene bilayer with a relative small
angle rotation between the layers and calculate the electronic structure near
zero energy in a continuum approximation. Contrary to what happens in a AB
stacked bilayer and in accord with observations in epitaxial graphene we find:
(a) the low energy dispersion is linear, as in a single layer, but the Fermi
velocity can be significantly smaller than the single layer value; (b) an
external electric field, perpendicular to the layers, does not open an
electronic gap
