Robuta

https://www.novuslight.com/world-s-first-commercial-optical-quantum-clock_N13597.html

https://www.nist.gov/publications/testing-stability-fundamental-constants-199-hg-single-ion-optical-clock

https://csoc-project.eu/index.php/login

https://www.nist.gov/publications/systematic-study-87sr-clock-transition-optical-lattice

https://physicsworld.com/a/new-definition-of-second-ticks-closer-after-international-optical-clock-comparison/