> We are in need of a reference crystall with a swing of about +-1200 PPM at
> Fc of 16MHz and a couple other frequencie in that range.  Obviously, 10PPM
> is not acceptable.  Thanks for the response nonetheless.
> 
> -Vincent Deno

So, what you want is a temperature sensor that changes 19200 Hz/¡C
running in a base frequency of 16MHz.  That margin of high ppm is also
directly related with (somehow) bad quality of components, and probably
you will not get a steady and linear response, with lots of differences
from one component to another.  Probably you should go to measure that
temperature using some other technique.
Wagner