1. Mindlin, R.D.: Polarization gradient in elastic dielectrics. Int. J. Solids Struct. 4, 637–642 (1968)
2. Tagantsev, A.K.: Theory of flexoelectric effect in crystals. Zhurnal Eksp. Teor. Fiz. 88, 2108–2122 (1985)
3. Tagantsev, A.K.: Piezoelectricity and flexoelectricity in crystalline dielectrics. Phys. Rev. B. 34, 5883–5889 (1986)
4. Tolpygo, K.B.: Physical properties of the salt lattice constructed from deforming ions. J Exp Theor PhysUSSR. 20, 497 (1950)
5. Tolpygo, K.B.: Physical properties of a rock salt lattice made up of deformable ions. Ukr. J. Phys. 53, 93–102 (2008)