1. H. B. Rosenstock, Phys. Rev. 121, 416 (1961).PHRVAO0031-899X
2. W. Ledermann, Proc. Roy. Soc. A182, 362 (1944).
3. M. Born and K. Huang, Dynamic Theory of Crystal Lattices (Oxford University Press, London, 1954), Appendix IV, p. 391.
4. D. C. Gazis and R. F. Wallis, J. Math. Phys. 3, 190 (1962).JMAPAQ0022-2488
5. E. W. Montroll and R. B. Potts, Phys. Rev. 100, 525 (1955).PHRVAO0031-899X