Philip Hartman

Philip Hartman (May 16, 1915 – August 28, 2015) was an American mathematician at Johns Hopkins University working on differential equations who introduced the Hartman–Grobman theorem. He served as Chairman of the Mathematics Department at Johns Hopkins for several years. He has an Erdös number of 2.
His book gives a necessary and sufficient condition for solutions of ordinary initial value problems to be unique and to depend on a class C1 manner on the initial conditions for solutions.
He died in August 2015 at the age of 100.