Correspondence about stage lighting and simultaneous interpretation, September 1959 to March 1962 Date: September 1959 to March 1962
Correspondence between Ashworth and Utzon, Ove Arup and others,, June 1960 to December 1961 Date: June 1960 to December 1961
Correspondence between Ashworth, the Opera House Executive Committee, Utzon and others, July 1964 - April 1966