1. M. Born: Dynamik der Kristallgitter (Leipzig 1915) Chap.3
2. M. Born, K. Huang: Dynamical Theory of Crystal Lattices (Clarendon, Oxford 1954)
3. L.D. Landau, E.M. Lifshitz: Quantum Mechanics — Nonrelativistic Theory (Nauka, Moscow 1974) [in Russian]
4. G. Ya. Lyubarsky: Group Theory and Its Application in Physics (Fizmatgiz, Moscow 1958) [in Russian]
5. S.I. Pekar: Zh. Eksp. Teor. Fiz. 36, 451 (1959) [English transl.: Sov. Phys. JETP 9, 314 (1959)]