“…Another relevant physical object of this kind is a system of apex oxygen ions in YBaCuO-type high-temperature superconductors, see [27,57,74,75]. Quantum anharmonic oscillators are also used in models describing interaction of vibrating quantum particles with a radiation (photon) field, see [32,33,58], or strong electronelectron correlations caused by the interaction of electrons with vibrating ions, see [25,26], responsible for such phenomena as superconductivity, charge density waves etc. Finally, we mention systems of light atoms, like Li, doped into ionic crystals, like KCl.…”