1. On the ratio of the first two eigenvalues of Schrödinger operators with positive potentials;Ashbaugh, Mark S.,1987
2. [AB2] M. S. Ashbaugh and R. D. Benguria, Sharp bound for the ratio of the first two eigenvalues of Dirichlet Laplacians and extensions (in preparation).
3. Monographs and Studies in Mathematics;Bandle, Catherine,1980
4. Bounds for the ratios of the first three membrane eigenvalues;Brands, J. J. A. M.;Arch. Rational Mech. Anal.,1964
5. A general rearrangement inequality for multiple integrals;Brascamp, H. J.;J. Functional Analysis,1974