question: What was the topic of Von Neumann 's work at Princeton in 1931 - 32 ?
answer: ergodic theorem
turker_answer: The ergodic theorem was the topic of Von Neumann 's work at Princeton in 1931 - 32 .
rule-based: The topic of Von Neumann 's work at Princeton in 1931 - 32 was ergodic theorem .