Crystal oscillators are loosely divided through the frequency they operate at and whether they are essential oscillators—operate in the frequency marked within the can or at even multiples of that (overtone oscillators). Modeling of nonlinear micromechanical resonators as well as their simulation With all the harmonic‐equilibrium method 的很多特性，如温度稳定性，老化稳定性，等效电路参... https://social4geek.com/story4525010/a-review-of-bulk-crystal-oscillator