The Sources of Kolmogorov's Grundbegriffe
  Andrei Kolmogorov's Grundbegriffe der Wahrscheinlichkeits-rechnung put probability's modern mathematical formalism in place. It also provided a philosophy of probability--an explanation of how the formalism can be connected to the world of experience. In this article, we examine the sources of these two aspects of the Grundbegriffe--the work of the earlier scholars whose ideas Kolmogorov synthesized. 
Glenn Shafer, Vladimir Vovk