LTZ1000
Production
The LTZ1000 and LTZ1000A are ultra stable temperature controllable references. They are designed to provide 7V outputs with temperature drifts of 0.05ppm...
Datasheet
LTZ1000 on Analog.com
A voltage reference’s main purpose is to provide a known output, and accuracy and stability are the most important aspects of this. ADI’s article “March 2009 - How to Choose a Voltage Reference (analog.com)” describes different types of references and how to select the best reference for your application.