sentences:  The London 1980 Exhibition card, issued 9 April 1980 to commemorate the 1980 International Stamp Exhibition, and the set of five cards for London Landmarks, issued 7 May 1980, both had the reference number PHQ43.The set of five cards for Gallantry, issued 11 September 1990, and the set of four cards for Astronomy, issued 16 October 1990, both had the reference number PHQ129.Consequently, the number PHQ130 was unused.