Bonn, 16 February 1956 - Institutional correspondence Antonio Mª Aguirre's letter to Alberto Martín-Artajo Álvarez
New York, 24 September 1957 - Institutional correspondence Virginia Pearson's letter to Alfred H. Barr Jr.
New York, 5 November 1957 - Institutional correspondence Virginia Pearson's letter to Katharine Kuh, dated 5 November 1957
New York, 20 September 1957 - Institutional correspondence Virginia Pearson's letter to Katharine Kuh, dated 20 September 1957