https://en.wikipedia.org/wiki/Oskar_R._Lange#/media/File:Oskar_Lange_20-65.jpg
Source of above picture: Władysław Miernicki – Narodowe Archiwum Cyfrowe, Sygnatura: 20-65
Lange’s affidavit to support Leo’s immigration application:
lange_nov1_1939
Lange’s letter in support of Leo’s financial aid application:
lange1941_hurwicz