What Greek mathematician who spend most of his professional life in Germany lends his name to the Vitali–Carathéodory theorem?
Vitali–Carathéodory theorem:  It is named after Giuseppe Vitali and Constantin Carathéodory. Constantin Carathéodory: Constantin Carathéodory (Greek: Κωνσταντίνος Καραθεοδωρή "Konstantinos Karatheodori"; 13 September 1873 – 2 February 1950) was a Greek mathematician who spent most of his professional career in Germany.
Constantin Carathéodory