1. A. M. Hall and C. J. Slunder: The Metallurgy, Behavior, and Application of the 18-Percent Nickel Maraging Steels, NASA Report SP-5051, 1968.
2. G. W. Tufnell and R. F. Cairns:ASM Trans. Quart., 1968, vol. 61, p. 798.
3. C. S. Carter:Met. Trans., 1970, vol. 1, p. 1551.
4. S. Floreen: Met. Rev., vol. 126, Metals and Materials, September 1968, p. 115.
5. Proposed Method of Test for Plane Strain Fracture Toughness of Metallic Materials, ASTM Stand, May, 1969, Pt. 31, p. 1099.