1. On the Green's function of an N-point boundary value problem;Beesack;Pacific J. Math.,1962
2. On an inequality of P. R. Beesack;Nehari;Pacific J. Math.,1964
3. On Green's function of an N-point boundary value problem;Das;Trans. Amer. Math. Soc.,1973
4. Boundary value problems for ordinary differential equations;Jackson,1977
5. Disconjugacy;Coppel,1971