1. M. I. Klinger and V. G. Karpov, Self-trapping of electron pairs in structures with tunnelling states (local centers with inter-electron attraction), Pisma v Zh. Tekh. Fiz., 6:1473–1478 (1980).
2. M. I. Klinger and V. G. Karpov, Self-trapping of electron pairs in materials with tunnelling states. Electrons in perfect covalent glasses, Sol. State Comm., 37:975–978 (1981).
3. V. G. Karpov and M. I. Klinger, On the possible origin of atomic tunnelling states in covalent glasses, Pisma v Zh. Tekh. Fiz., 6:1478–1483 (1981).
4. M. I. Klinger and V. G. Karpov, Spectral and thermodynamic properties of electrons in mobility gap states, Sol. State Comm., 29:329–332 (1981).
5. P. W. Anderson, B. I. Halperin and C. M. Varma, Anomalous low-temperature thermal properties of glasses and spin glasses, Phil. Mag., 25:1–9 (1972).