I. V. Vovchenko, V. Yu. Shishkov, A. A. Zyablovsky, E. S. Andrianov, “Model for the description of the relaxation of quantum-mechanical systems with closely spaced energy levels”, Pis'ma v Zh. Èksper. Teoret. Fiz., 114:1 (2021), 43–49; JETP Letters, 114:1 (2021), 51–57