Madrid, 2 December 1975 and Berkeley, California, 8 January 1976 - Institutional correspondence A letter from José Mario Armero to Herschel B. Chip, with reply
1988-1989 - Institutional correspondence Correspondence related to the Guernica exhibition project at the Museum Boymans-van Beuningen in Rotterdam
Philadelphia, 3 May 1939 - Institutional correspondence The Medical Bureau and North American Committee's letter to the Exhibition Committee