1) A. Brandtzaeg & Others : “The Failure of Plain and Spirally Reinforced Concrete in Compression”, Bulletin No. 190, University of Illinois Engineering Experiment Station, Urbana, Ill., Apr. 1929
2) R. Jones : “A Method of Studying the Formation of Cracks in a Material Subjected to Stresses”, British Journal of Applied Physics (London), Vol. 3, No. 7, July 1952, pp. 229-232