Cotlar's inequality without the doubling condition and existence of principal values for the Cauchy integral of measures

We give a complete geometric characterization of those positive measures mu on C such that for any complex finite measure v on C the principal value of the Cauchy integral of v, lim(epsilon-->0) integral(\y-x\>epsilon) 1/y-x dv(y), exists for mu-almost all x is an element of C. We also prove that the classical Cotlar's inequality holds for Calderon-Zygmund operators without assuming that the underlying measure on C is doubling. This allows us to show that the standard arguments for the L-p and weak (1,1) boundedness of the maximal operator work in this case with some slight modifications.