Algorithm 775: The Code SLEUTH for Solving Fourth-Order Sturm-Liouville Problems. - Leon Greenberg; Marco Marletta (ACM Trans. Math. Softw., 1997)

Numerical Solution of Non-Self-Adjoint Sturm-Liouville Problems and Related Systems. - Leon Greenberg; Marco Marletta (SIAM J. Numer. Anal., 2001)