New York, 16 October 1981 - Institutional correspondence John Koegel's letter to Javier Tusell, dated 16 October 1981
New York, 16 October 1981 - Institutional correspondence John Koegel's letter to Javier Tusell, dated 16 October 1981
New York, 16 October 1981 - Institutional correspondence John Koegel's letter to Javier Tusell, dated 16 October 1981
30 October 1981 - Institutional correspondence John Koegel's letter to Richard E. Oldenburg, dated 30 October 1981
Amsterdam, 6 July 1956 - Institutional correspondence A letter from J. M. Trias de Bes to Alberto Martín-Artajo Álvarez
New York, 31 August 1981 - Institutional correspondence John Koegel's letter to Richard E. Oldenburg, dated 31 August 1981