  In Phys. Rev. D 78 (2008) 104018 [arXiv:0807.1481], the conclusion that
"entropy eigenvalues of GB black hole are discrete and equally spaced, but the
area spacing is not equidistant" was firstly presented by Kothawala,
Padmanabhan and Sarkar. In this paper, using the new physical interpretation of
quasinormal modes proposed by Maggiore, we calculate the quantum spectra of
entropy for various types of non-rotating black holes with no charge. The
spectrum is obtained by imposing Bohr-Sommerfeld quantization condition to the
adiabatic invariant quantity. We conjecture that the spacing of entropy
spectrum is equidistant and is independent of the dimension of spacetime.
However, the spacing of area spectrum depends on gravity theory. In Einstein's
gravity, it is equally spaced, otherwise it is non-equidistant. This conjecture
agrees with the result of Kothawala, Padmanabhan and Sarkar.
