On the generators of the kernels of hyperbolic group presentations

In this paper we prove that if $\mathcal R$ is a (not necessarily finite) set of words satisfying certain small cancellation condition in a hyperbolic group $G$ then the normal closure of $\mathcal R$ is free. This result was first presented (for finite set $\mathcal R$) by T. Delzant [Delz] but the proof seems to require some additional argument. New applications of this theorem are provided.