Kepler, T.B. & Oprea, M. Improved inference of mutation rates: I. An integral representation of the Luria-Delbruck distribution.
Theoretical Population Biology 59, 41-48 (2001) (pdf).

Oprea, M. & Kepler, T.B.  Improved inference of mutation rates: II. Generalization of  the Luria-Delbruck distribution for realistic cell-cycle time distributions.
Theoretical Population Biology 59, 49-59 (2001) (pdf).