1. Wigner, E. P.: Group Theory and Application to Quantum Mechanics of Atomic Spectra. New York: Academic Press 1959.
2. Hamermesh, M.: Group Theory. Reading, Mass.: Addison-Wesley Publ. Inc. 1962.
3. Birman, J. L.: Group Theory Methods and Techniques with Applications to Physics. New York: J. Wiley & Sons Inc. (In preparation.)
4. Born, M., and K. Huang: Dynamical Theory of Crystal Lattices. Oxford: University Press 1954.
5. Leibfried, G., in: this Encyclopedia vol. VII, part 1, p. 104. Berlin-Göttingen-Heidelberg: Springer 1955.