1. Nagamiya, T., Yosida, K., Kubo, R.: Adv. Phys. 4 (1955) 1.
2. Keffer, F.: Spin waves, in: Encyclopedia of Physics, Flügge, S. (ed.), Berlin: Springer-Verlag, 1966, Vol. XVIII/2, p. 249.
3. de Jongh, L.J., Miedema, A.R.: Adv. Phys. 23 (1974) 1.
4. Arts, A.F.M., de Wijn, H.W.: Spin Waves in two-dimensional magnetic systems, theory and applications, in: Magnetic Properties of Layered Transition Metal Compounds, de Jongh, L.J. (ed.), Dordrecht: Kluwer Academic, 1990, p. 191.
5. Hirakawa, K., Ikeda, H.: Neutron scattering experiments on two-dimensional Heisenberg and Ising magnets, in: Magnetic Properties of Layered Transition Metal Compounds, de Jongh, L.J. (ed.), Dordrecht: Kluwer Academic, 1990, p. 231.