Introduction.- Part I - Superlinear indefinite problems.- Dirichlet boundary conditions.- More general nonlinearities f(t; s).- Neumann and periodic conditions: existence results.- Neumann and periodic conditions: multiplicity results.- Subharmonic solutions and symbolic dynamics.- Part II - Super-sublinear indefinite problems.- Existence results.- High multiplicity results.- Subharmonic solutions and symbolic dynamics.- Part III - Appendices.- Leray-Schauder degree for locally compact operators.- Mawhin's coincidence degree.- Maximum principles and a change of variable.- Bibliography. ukryj opis