The 2 oscillator circuits below are suited to using crystal oscillators in sequence or parallel mode: Substantial-repetition-rate and large-electric power picosecond regenerative amplifier according to an individual bulk Nd:GdVO4 crystal A timing reference incorporating one-crystal-silicon micromechanical resonator with an excellent aspect of greater than one million and a resonant fr... https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html