Amsterdam, 6 July 1956 - Institutional correspondence A letter from J. M. Trias de Bes to Alberto Martín-Artajo Álvarez
New York, 3 September 1981 - Internal institutional documents Inventory and conservation report on the works collected by New York's Museum of Modern Art to be sent to Spain
New York, 8 September 1981 - Internal institutional documents A confidential and private document signed by Álvaro Martínez-Novillo and José María Cabrera in New York