Copenhagen, 31 October 1956 - Institutional correspondence Lars Rostrup Boyesen's letter to Pablo Picasso
Copenhagen, 31 October 1956 - Institutional correspondence Lars Rostrup Boyesen's letter to Daniel-Henry Kahnweiler
Copenhagen, 31 October 1956 - Institutional correspondence Lars Rostrup Boyesen's letter to the Museum of Modern Art, New York
Paris, 10 December 1975 - Institutional correspondence Miguel de Lojendio's letter to Spain's Ministry of Culture