  We emphasize that there exist four Dirac-type points in the electron-energy
spectrum of a graphite bilayer near the point K of its Brillouin zone. One of
the Dirac points is at the point K, and three Dirac points lie nearby. Each of
these three points generates the Berry phase $\pi$, while the Dirac point at K
gives the phase $-\pi$. It is these four points that determine the Berry phase
in the bilayer. If an electron orbit surrounds all these points, the Berry
phase is equal to $2\pi$.
