The two oscillator circuits underneath are suitable for working with crystal oscillators in series or parallel manner: Substantial-repetition-level and higher-electric power picosecond regenerative amplifier based on an individual bulk Nd:GdVO4 crystal A timing reference incorporating only one-crystal-silicon micromechanical resonator with a high quality issue of larger sized than one... https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html