I.N. Adamenko, E. K. Nemchenko, and K. E. Nemchenko, Phonon model of heat radiation into superfluid helium by a solid with a flat surface (Review Article), Low Temp. Phys. 47, (2021) [Fiz. Nizk. Temp. 47, 703-709, (2021)] DOI: https://doi.org/10.1063/10.0005552.