Calder\'{o}n commutators and the Cauchy integral on Lipschitz curves revisited III. Polydisc extensions

This article is the last in a series of three papers, whose scope is to give new proofs to the well known theorems of Calder\'{o}n, Coifman, McIntosh and Meyer. Here we extend the results of the previous two papers to the polydisc setting. In particular, we solve completely an open question of Coifman from the early eighties.