New York, 10 February 1956 - Institutional correspondence A letter from Louise A. Boyer to Petro (Nelly) Van Doesburg
16 November 1939 - Personal correspondence A letter from Francisco De Troya to Pablo Picasso, dated 16 November 1939
23 November 1939 - Personal correspondence Francisco de Troya's letter to Pablo Picasso, dated 23 November 1939