Flushing, New York, 23 May 1939 - Institutional correspondence Simon Guggenheim's and Dana C. Backus's form letter to ask for donations
New York, 6 May 1955 - Institutional correspondence A letter from W.R. Keating & Company International to R. Lerondelle
New York, 23 January 1957 - Transport documents A letter from the vice-president of W. R. Keating & Company to Willem Sandberg