Lawless, G. F. (1987): Negative binomial and mixed Poisson regression. In: The Canadian Journal of Statistics Vol. 15 / No. 3, S. 209-215. Breslow, N. (1984): Extra-Poisson variation in log-linear models. In: Appl. Stat. 33, S. 38-44. Margolin, B. H., Kaplan, N., Zeiger, E. (1981): Statisical analysis of the Ames salmonella / microsome test. In: Proc. Nat. Acad. Sci. U.S.A. 76, S. 3779-3783.