1. U.S. patent No. 3,678,570 by Duvall, Owczarski, and Paulonis.
2. K. Harris, G. L. Erickson, and R. E. Schwer, “Directionally solidified and single-crystal superalloys”, Metals Handbook 10th edition, Vol. 1, ASM International, 1990. pp.995–1006.
3. G. L. Erickson, “Superalloys resist hot corrosion and oxidation,” Advanced Materials and Processes, Vol. 151, No. 3, 1997. pp. 27–30.
4. Related effects were also observed in ultrasonic imaging of flaws in anisotropic graph ite epoxy laminates. See, A. Minachi, F. J. Margetan and D. K. Hsu, “Delamination sizing in composite materials using a Gauss-Hermite beam model,” Ultrasonics, Vol 31, No 4, 1993. pp. 237–243.