The two oscillator circuits underneath are suitable for working with crystal oscillators in series or parallel method: High-repetition-fee and superior-electrical power picosecond regenerative amplifier based upon a single bulk Nd:GdVO4 crystal A timing reference incorporating an individual-crystal-silicon micromechanical resonator with an outstanding factor of greater than a million ... https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html