  The entropy-area spectrum of a black hole has been a long-standing and
unsolved problem. Based on a recent methodology introduced by two of the
authors, for the black hole radiation (Hawking effect) as tunneling effect, we
obtain the entropy spectrum of a black hole. In Einstein's gravity, we show
that both entropy and area spectrum are evenly spaced. But in more general
theories (like Einstein-Gauss-Bonnet gravity), although the entropy spectrum is
equispaced, the corresponding area spectrum is not.
