M. M. Bogdan and O. V. Charkina, Generation of wave packets and breathers by oscillating kinks in the sine-Gordon system, Low Temp. Phys. 47, 155–165, (2021) [Fiz. Nizk. Temp. 47, 173-184, (2021)] DOI: https://doi.org/10.1063/10.0003177.