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I. Ya. Fugol, V. N. Samovarov, and M. Yu. Libin, Dynamics of electronic excitations in YBCO at low temperatures, Low Temp. Phys. 25, (1999) [Fiz. Nizk. Temp. 25, 459-468, (1999)] DOI: https://doi.org/10.1063/1.593746.