This page is devoted to the pursuit of Precision Timing; the instruments, techniques and methods that contribute to this science.
Visit Bruce Griffiths' Precision Time and Frequency pages.
There is a lot of timing related information in the Wiki too, check it here.
The Manual pages have a section dedicated to Precision Timing.
If you are considering or interested in building your own GPSDO, make sure to check Attila Kinali's page
I have also assembled some information about precision timing, time and frequency standards and related topics.