Alfred Tarski

Alfred  Tarski
Polish mathematician Alfred Tarski (1901-83) ranks among the greatest logicians of all time. Best known for his work on model theory, meta mathematics, and algebraic logic, he contributed to many other fields of mathematics and taught at the University of California, Berkeley, for more than 40 years.
Tarski's student Andrzej Mostowksi worked at the University of Warsaw on first-order logic and model theory.
Tarski's University of California colleague Raphael M. Robinson built on Tarski's concept of essential undecidability and proved a number of mathematical theories undecidable.