Yu.M. Shukrinov, H. Azemtsa-Donfack, I.R. Rahmonov, and A.E. Botha, Cascade of parametric resonances in coupled Josephson junctions, Low Temp. Phys. 42, (2016) [Fiz. Nizk. Temp. 42, 573-580, (2016)] DOI: https://doi.org/10.1063/1.4954777 .