IMBEDDING C-1 INTO H-1

This article gives a direct proof of Theorem 7.58 of Greiner [4]. This result implies that the classical Mikhlin-Calderon-Zygmund calculus f or the principal value convolution operators on C is, in a natural way , the limit of the Laguerre calculus for principal value convolution o perators on H-1 = C x R.