1. Alternative problems for nonlinear functional equations;Bancroft;J. diff. Eqns,1968
2. Functional analysis and periodic solutions of nonlinear differential equations;Cesari;Contr. diff. Eqns,1963
3. Functional analysis and Galerkin's method;Cesari;Mich. math. J.,1964
4. Ordinary Differential Equations;Hale,1969
5. Applications of alternative problems;Hale,1971