T. Matsuo and H. Suzuki: J. Phys. Soc. Japan 41 (1976) 1692.
P. G. Klemens: Proc. Phys. Soc. A68 (1955) 1113.
P. Gruner and H. Bross: Phys. Rev. 172 (1968) 583.
F. R. N. Nabarro: Proc. Roy. Soc. A209 (1951) 278.
T. Ninomiya: Fundamental Aspects of Dislocation Theory, ed. A. Simmons et al. (National Bureau of Standards Special Publication 317, 1970) Vol. 1, p. 315.