Guo, Ding Hui Estimation of the eigenvalues of a system of degenerate second-order equations. (Chinese) Zbl 1039.35508 Math. Model. Comput. Exp. 9, No. 1, 69-74 (1996). MSC: 35P15 Estimates of eigenvalues in context of PDEs 58J50 Spectral problems; spectral geometry; scattering theory on manifolds PDFBibTeX XMLCite \textit{D. H. Guo}, Math. Model. Comput. Exp. 9, No. 1, 69--74 (1996; Zbl 1039.35508)