In 1949 he published a work, jointly with Kolmogorov, Limit Distributions for Sums of Independent Random Variables which contains a description of much of his early research.
Sa 1949 siya nai-publish ng isang trabaho, sama-sama sa Kolmogorov, Limit Distributions para sa Sums ng Independent Random variable na naglalaman ng isang paglalarawan ng marami ng kanyang unang bahagi ng pananaliksik.