Andrey V. Chubukov and Dmitry Mozyrsky, Evolution of the dynamics of neutral superconductors between BCS and BEC regimes: the variational approach, Low Temp. Phys. 44, (2018) [Fiz. Nizk. Temp. 44, 684-690, (2018)] DOI: https://doi.org/10.1063/1.5037555.