Moon Phases (University of Texas McDonald Observatory) National Association of Watch and Clock Collectors NAWCC Great Southwestern Chapter 15 American Watchmakers-Clockmakers Institute A Walk Through Time (NIST) A History of Horology, Clockmaking, and Watches Savage and Polite's Antique Clocks Identification and Pricing Guide Mike's Clock Clinic (Mike Murray) Abbey Clock Clinic (Mark Headrick) How a clock works