Doug's Atomic Clocks - Details on Doug Hogarth's experiments with his atomic clock. www.niceties.com/atomic.html
How Stuff Works: Atomic Clock - Concise history, background, definitions and operational information regarding atomic clocks. www.howstuffworks.com/atomic-clock.htm
How Stuff Works: Pendulum Clock - Concise description using drawings and animation to show the operation of a pendulum clock. www.howstuffworks.com/clock.htm
