  We study the quantum Hall effect (QHE) in graphene based on the current
injection model. In our model, the presence of disorder, the edge-state
picture, extended states and localized states, which are believed to be
indispensable ingredients in describing the QHE, do not play an important role.
Instead the boundary conditions during the injection into the graphene sheet,
which are enforced by the presence of the Ohmic contacts, determine the
current-voltage characteristics.
