Madrid, 21 February 1969 - Institutional correspondence Florentino Pérez-Embid's letter to Joaquín de la Fuente
Chicago, 11 October 1939 - Institutional correspondence Charles Goodspeed's telegram to Pablo Picasso
Gerti Fietzek (ed.), Cologne: Buchhandlung Walther König, 2009 - Essay Maria Eichhorn. The Artist's Contract