  This paper uses convolutions of the gamma density and the one-sided stable
density to construct higher level densities. The approach is applied to
constructing a 4-parameter Mittag-Leffler density, whose Laplace transform is a
corresponding Mittag-Leffler function, which is completely monotone (CM) by
construction. Laplace transforms of mixtures of the stable densities with
respect to the 4-parameter Mittag-Leffler distribution are compositions of the
Mittag-Leffler functions with Bernstein functions, thereby generating a rich
family of CM variants of the base CM Mittag-Leffler functions, including known
instances as special cases.
