Complex sentence: The Piast Institute is a national institute for Polish and Polish-American affairs that was started in 2003 by Dr. Thaddeus Radzilowski and Virginia Skrzyniarz.
Split into simpler sentences: The Piast Institute is a national institute for Polish and Polish-American affairs. It was started in 2003 by Dr. Thaddeus Radzilowski and Virginia Skrzyniarz.