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In Vienna where did Kurt Gödel study?
At the age of 18, Kurt Gödel joined his brother in Vienna and entered the University of Vienna.
What year did Kurt Gödel start studying?
In 1924, Kurt Gödel aged 18 entered the University of Vienna.

Question: What was his major, or field of study?
Self-contained rewrite: What was Kurt Gödel's major, or field of study?