A. Ya. Fishman, V. Ya. Mitrofanov, V. I. Tsidilkovski, “Orientationally degenerate (OH)$^-$ centers in perovskite-type proton-conducting oxides: Low-temperature thermodynamics and H/D isotope effects”, Pis'ma v Zh. Èksper. Teoret. Fiz., 83:3 (2006), 133–137; JETP Letters, 83:3 (2006), 103–108
