Answer by periblepsis for Crystal oscillator based on a differential pair of npn transistors does not oscillate

The basic idea will be something like this:

^{simulate this circuit– Schematic created using CircuitLab}

It's not a complete design and I used \$5\:\text{V}\$ here. (I'd recommend keeping the \$10\,\text{mA}\$ current sink but adjust the biasing as appropriate for other rail voltages.)

The duty cycle won't be a perfect 50%.

Using very low Q, only 2000 for this example, LTspice shows this (the outputs are taken from the two collectors):

(Higher Q works well, of course.)

This would not be a final design. If for no other reason then because the output likely needs buffering before it drives some other circuit. But it is a demonstration of the behavioral topology to use as a basis.