Temperature Compensating a Colpitts Crystal Oscillator

Hi,

I am trying to temperature compensate a Colpitts crystal oscillator circuit by making a modification to the one found here:

http://www.radio-electronics.com/info/circuits/transistor_crystal_oscillator/crystal_oscillator.php

I know that you can use thermistors to do so, but I have no idea how to select component values. I am using a 6 MHz crystal made by INFICON.

Could anyone point me in the direction of a good tutorial for selecting components please?

I'd be grateful for any help you could give.

Many thanks

hooch254