22, 1940. On May 7 the Dutch minister of education appointed Rosenfeld to succeed Uhlenbeck at the University of Utrecht. On May 8 Pais wrote to Rosenfeld at Liège to ask if he might continue his studies under him if his appointment came through, and again on May 9 to congratulate him on his appointment. On May 10, 1940, the Germans invaded the Netherlands, Belgium, and Luxembourg, disrupting the mail between Utrecht and Liège for months.

After mail service was restored, Pais again wrote to Rosenfeld in Liège. In the meantime Pais