Eigenvalue approximations for linear periodic differential equations with a singularity. Harris, B.J., Marzano, F. (1999) Electronic Journal of Qualitative Theory of Differential Equations [electronic only]
Eigenvalue comparisons for boundary value problems of the discrete beam equation. Ji, Jun, Yang, Bo (2006) Advances in Difference Equations [electronic only]
Eigenvalue comparisons for differential equations on a measure chain. Chyan, Chuan Jen, Davis, John M., Henderson, Johnny, Yin, William K.C. (1998) Electronic Journal of Differential Equations (EJDE) [electronic only]
Eigenvalue computations for regular matrix Sturm-Liouville problems. Dwyer, H.I., Zettl, A. (1995) Electronic Journal of Differential Equations (EJDE) [electronic only]
Estimates for the Eigenvalues of Hill's Equation and Applications for the Eigenvalues of the Laplacian on Toroidal Surfaces. Brigitte Beekmann, Hermann Lökes (1990) Manuscripta mathematica
Extremal properties of eigenvalues for a metric graph Leonid Friedlander (2005) Annales de l’institut Fourier We establish the sharp lower bound for eigenvalues of a metric graph.