Table of contents : Introduction....Pages 1-3 Alternative problems : An historical perspective....Pages 4-9 Coincidence degree for perturbations of Fredholm mappings....Pages 10-25 A generalized continuation theorem and existence theorems for Lx = Nx....Pages 26-35 Two-point boundary value problems : Nonlinearities without special structure....Pages 36-103 Approximation of solutions — The projection method....Pages 104-133 Quasibounded perturbations of Fredholm mappings....Pages 134-150 Boundary-value problems for some semilinear elliptic partial differential equations....Pages 151-165 Periodic solutions of ordinary differential equations with quasibounded nonlinearities and of functional differential equations....Pages 166-188 Coincidence index, multiplicity and bifurcation theory....Pages 189-208 Coincidence degree for k-set contractive perturbations of linear Fredholm mappings....Pages 209-228 Nonlinear perturbations of fredholm mappings of nonzero index....Pages 229-241