Existence results are established for the equation y '' +f(t, y) = 0, 0 < t < 1. Here f may be singular in y and f is allowed to change sign. Our boundary data include y(0) = y'(1) + ky(1) = 0, k > -1 and y(0) = ...

We present continuation results for operators between locally convex linear topological spaces. These results will then be applied to obtain existence principles for differential equations on semi-infinite intervals.

The Schauder Tychonoff theorem in a locally convex topological space is used to establish existence results for Volterra-Hammmerstein and Hammerstein integral equations in a reflexive Banach space.

We extend a fixed-point theorem of Reinermann [1] for the sum of two operators. Our results are then used to establish new existence results for differential equations in Banach spaces.

Topological results for set valued maps are used to establish existence results for integral inclusions of Volterra or Hammerstein type.