Research in support of the 1971 revision of BS 368 : precast concrete flags /
Cornelius, D. F.
Kollek, J. J.
Teychenné, David Clayton.
Garston :  Building Research Establishment, 
1973.
Reprinted from Precast concrete, vol. 3, no. 1, January 1972 and vol. 3, no. 2, February 1972.