> Time Too Good to Be True, Daniel Kleppner > Physics Today, March 2006, page 10 > https://physicstoday.scitation.org/doi/10.1063/1.2195297 An adventure in relative time-keeping, Tom Van Baak Physics Today, March 2007, page 16 https://physicstoday.scitation.org/doi/10.1063/1.2718741 /tvb