How can one prove that the convolution of f \in L^1 and g \in L^p is defined almost everywhere? Here f and g are measurable functions in R^n.

In general what techniques are there for showing some function is defined a.e and where should I look for them in analysis literature.

## Background

This came up while I was reading some notes to understand harmonic analysis.

Basic real analysis. – Mariano Suárez-Alvarez♦ Mar 17 '10 at 15:01