rubidium freqnency standard
rubidium frequency standard
~(87)Rb atomic frequency standard
atomic frequency standard
Passive Rubidium Atomic Clock
Rubidium Atomic Oscillator
Rubidium Vapor Cell Frequency Standard
rubidium-vapor frequency standard
space-borne rubidium atomic clock
atomic beam frequency standard
atomic frequency-stabilized laser
cesium atomic beam frequency standard
atomic-bram frequency standard
ammonium molecular beam frequency standard
BSF Basic Standard Frequency