The 2 oscillator circuits under are suitable for employing crystal oscillators in series or parallel method: Higher-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 excellent factor of greater than a million in additio... https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html