1. Every second counts
2. Audoin, C. and Guinot, B., [The Measurement of Time: Time, Frequency and the Atomic Clock], Cambridge University Press, Cambridge & New York, 1–5 (2001).
3. Spectrum Instruments Inc., “Summary of Time and Frequency Systems Features and Capabilities,” www.spectruminstruments.net/lit/Summary.pdf (29 September 2016).
4. Time and Frequency Measurements Using the Global Positioning System;Lombardi,2001