Amsterdam, 6 July 1956 - Institutional correspondence A letter from J. M. Trias de Bes to Alberto Martín-Artajo Álvarez
May - July 1992 - Institutional correspondence Loaned works at the Museo Nacional Centro de Arte Reina Sofía in conjunction with the rearrangement of holdings between the Reina Sofía and Museo Nacional del Prado
Madrid, 8 February 1995 - Internal institutional documents A loan approval form for the exhibition Picasso: The Love and the Anguish. The road to Guernica