APA (7th ed.) Citation

Essen, R. (2013). Two clocks that changed the world: The birth of atomic timekeeping.

Chicago Style (17th ed.) Citation

Essen, Ray. Two Clocks That Changed the World: The Birth of Atomic Timekeeping. 2013.

MLA (9th ed.) Citation

Essen, Ray. Two Clocks That Changed the World: The Birth of Atomic Timekeeping. 2013.

Warning: These citations may not always be 100% accurate.