The following seminal paper by the great Kolmogorov introduced the important statistical concept of Bayesian Sufficiency.
This paper is cited in diverse sources such as the standard textbook by Lehmann and Romano, Testing Statistical Hypotheses (2008) (p. 20) and Blackwell and Ramamoorthi's oft-cited paper A Bayes But Not Classically Sufficient Statistic (1982) (p. 1).
Kolmogorov wrote the paper in Russian. Despite its importance, it does not seem to have been translated into any other major European language (see here and here).
Would someone please translate the definition of Bayesian Sufficiency from Kolmogorov's paper, as well as, if possible, any pertinent definitions, theorems and examples?
The concept may not be termed 'Bayesian Sufficiency' in the article. Here's a concise definition of it, excerpted from Blackwell and Ramamoorthi's paper, to help identify the definition in Kolmogorov's paper.
Let $X$ be a random variable whose distribution $P_\theta$ depends on the parameter $\theta$, and let $Y$ be a function of $X$. [...] $Y$ is [Bayes] sufficient if for every prior distribution of $\theta$ the posterior distribution of $\theta$ given $X$ depends on $Y$ only.
More rigorous, measure-theoretic definitions of Bayesian sufficiency may be found here.
I'm particularly interested in finding out which, if any, of the two variations on the concept of Bayesian Sufficiency described in the last link matches Kolmogorov's original definition.