[3] P GILL. Optial frequency standards. Metrologia, 42, S125-S137(2005).
[24] Xingwen ZHAO, Haijun CHEN, Lin YANG et al. Stabilizing the optical frequency by laser-induced fluorescence in optically pumped Cs beam frequency standard. Journal of Astronautic Metrology and Measurement, 40, 17-22(2020).