The first volume in this subseries of the Encyclopaedia is meant tofamiliarize the reader with the discipline Commutative HarmonicAnalysis.
The second article focuses on some of the classical problems ofFourier series; it's a"mini-Zygmund"for the beginner. The thirdarticle is the most modern of the three, concentrating on singularintegral operators. It also contains an introduction to Calderon-Zygmund theory.