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
Museo Nacional Centro de Arte Reina Sofía, Madrid, October 19, 2018 - Interview Francis Frascina in conversation with Lucy Lippard