Zurich, 12 December 1955 - Institutional correspondence A letter from Klaus Herdeg to Willem Sandberg
Madrid, 12 Julio 1971 - Institutional correspondence A letter from Juan Antonio Cánovas del Castillo to Florentino Pérez-Embid
Madrid, 11 December 1979 - Institutional correspondence Marcelino Oreja's letter to Manuel Clavero Arévalo