1. Chavel, I., Eiqenvalues in Riemannian Geometry, New York: Academic Press, 1984.
2. Bérard, P. H.. Spectral Geometry: Direct and inverse problem, LNM, Vol. 1207, New York: Springer-Verlag, 1986.
3. Yau, S. T., Schoen, R., Differential Geometry (in Chinese), Beijing: Science Press, 1998.
4. Li, P., Lecture Notes on Geometric Analysis, Seoul: Seoul National Univ, Korea, 1993.
5. Ma, C. Y., The Spectrum of Riemannian Manifolds (in Chinese), Nanjing: Press of Nanjing University, 1993.