New York, 6 May 1955 - Institutional correspondence A letter from W.R. Keating & Company International to R. Lerondelle
New York, 23 January 1957 - Transport documents A letter from the vice-president of W. R. Keating & Company to Willem Sandberg
<em>Frieze</em>, London, no. 104 (January–February 2007), January 1, 2007 - Article “2nd Seville Biennial”