1. 1. Fisher, D. M. , Bubsey, R. T. and Srawley, J. E. , ‘Design and use of a displacement gage for crack extension measurements’, NASA TN-D-3724, National Aeronautics and Space Administration (1966).
2. 3. BS 5447:1977, ‘Methods of test plane strain fracture toughness (KIC) of metallic materials’, British Standards Institution (1977).