Erling Andersen: Sufficiency and Exponential Families for Discrete Sample Spaces. In: Journal of the American Statistical Association. 65. Jahrgang, Nr.331, September 1970, S.1248–1255, doi:10.2307/2284291.
B Koopman: On distribution admitting a sufficient statistic. In: Trans. Amer. math. Soc. 39. Jahrgang, 1936, S.399–409, doi:10.2307/1989758.
