  We show that the usual Mikhlin multiplier theorem relative to the distorted
Fourier transform holds in the range (3/2,3) at least for radial functions and
potentials. The restricted range is due to the fact that the Schroedinger
operator which gives rise to the distorted Fourier transform may have a zero
energy resonance. Consequently, the Littlewood-Paley theorem is shown also only
for the range (3/2,3).
