Madrid, 22 April 1976 - Internal institutional documents A report by Joaquín de la Puente on the ownership of Guernica and the negotiation possibilities with the Museum of Modern Art, New York
Madrid, 10 September 1981 - Internal museum documents Certificate for the reception of Guernica, and its stretcher and related works
New York: Praeger Publishers Inc., 1973 - Essay Six Years: The Dematerialization of the Art Object from 1966 to 1972