The 2 oscillator circuits under are suitable for employing crystal oscillators in series or parallel method: Substantial-repetition-rate and large-energy picosecond regenerative amplifier based upon a single bulk Nd:GdVO4 crystal A timing reference incorporating only one-crystal-silicon micromechanical resonator with a high quality variable of larger sized than one million as well https://ledbookmark.com/story4600160/the-2-minute-rule-for-bulk-crystal-oscillator