Chord Techniques and Newton's Method for Discrete Bifurcation Problems. E. Bohl (1980) Numerische Mathematik
Comparison between the variational iteration method and the homotopy perturbation method for the Sturm-Liouville differential equation. Neamaty, A., Darzi, R. (2010) Boundary Value Problems [electronic only]
Correction of Finite Element Estimates for Sturm-Liouville Eigenvalues. Alan L. Andrew, John W. Paine (1986/1987) Numerische Mathematik
Correction of Numerov's Eigenvalue Estimates. Alan L. Andrew, John W. Paine (1985) Numerische Mathematik