Czesław Ryll-Nardzewski

Czesław Ryll-Nardzewski (Polish: [ˈt͡ʂɛswav ˈrɨl narˈd͡zɛfskʲi]; 7 October 1926 – 18 September 2015) was a Polish mathematician.

Born in Wilno, Commonwealth of Poland, he was a student of Hugo Steinhaus. At the age of 26 he became professor at the Warsaw University. In 1959, he became a professor at the Wrocław University of Technology. His main research areas are measure theory, functional analysis, foundations of mathematics and probability theory. Several theorems bear his name: the Ryll-Nardzewski fixed point theorem, the Ryll-Nardzewski theorem in model theory, and the Kuratowski and Ryll-Nardzewski measurable selection theorem.

He became a member of the Polish Academy of Sciences in 1967. He died in 2015 at the age of 88.