We study a variety of scalar integro-differential equations with singular kernels including
linear, nonlinear, and resolvent equations. The first result involves a type of existence
theorem which uses a fixed point mapping defined by the integro-differential equation
itself and produces a unique solution with a continuous derivative in a very simple
way. We then construct a Liapunov functional yielding qualitative properties of solutions.
The work answers questions raised by Volterra in 1928, by Levin in 1963, and by
Grimmer and Seifert in 1975. Previous results had produced bounded solutions from
bounded perturbations. Our results mainly concern integrable solutions from integrable
perturbations.