Crystals above 30 MHz (around >200 MHz) are normally operated at sequence resonance the place the impedance appears at its bare minimum and equal for the series resistance. For these crystals the series resistance is specified ( It's important to notice that oscillators Use a crucial parameter—the resonant resistance (RR), https://getsocialselling.com/story4407982/the-5-second-trick-for-smd-crystal-oscillators