We revisit the Mittag-Leffler functions of a real variable t, with one, two
and three order-parameters {α,β,γ}, as far as their Laplace
transform pairs and complete monotonicty properties are concerned. These
functions, subjected to the requirement to be completely monotone for t>0,
are shown to be suitable models for non--Debye relaxation phenomena in
dielectrics including as particular cases the classical models referred to as
Cole-Cole, Davidson-Cole and Havriliak-Negami. We show 3D plots of the response
functions and of the corresponding spectral distributions, keeping fixed one of
the three order-parameters.Comment: 22 pages, 6 figures, Second Revised Versio