Crystal oscillators are loosely divided because of the frequency they perform at and whether they are essential oscillators—perform at the frequency marked to the can or at even multiples of that (overtone oscillators). Modeling of nonlinear micromechanical resonators and their simulation While using the harmonic‐equilibrium technique PDF Design of resonators https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html