Valentin Freilikher, Victor Kagalovsky, Yuri Kivshar, and Leonid Pastur, In memory of Sergey A. Gredeskul (1942–2023), Low Temp. Phys. 50, 1053–1056, (2024) [Fiz. Nyzk. Temp. 50, 1175-1178, (2024)] DOI: https://doi.org/10.1063/10.0034337.