1. DIN 17175, “Seamless steel tubes for elevated temperatures; technical terms of delivery” (Beuth Verlag GmbH, Berlin, Köln, 1979).
2. ASTM E813-81 “Standard Test Method forJ IC ; a Measure of Fracture Toughness”, Annual Book of ASTM Standards (American Society for Testing and Materials, Philadelphia, Pennsylvania, 1984).
3. P. UGGOWITZER and P. SIGRIST,Ber- undHüttenmännische Monatshefte 128 (3) (1983) 72.
4. F. DOBEŠ and K. MILIČKA,Met. Sci. 10 (1976) 382.
5. F. B. PICKERING,Iron Steel 41 (1968) 91.