„A Revolution in Timekeeping, part 3”. A Walk Through Time. NIST (National Inst. of Standards and Technology). 2002. Архивирано из оригинала 28. 5. 2007. г. Приступљено 28. 5. 2014.CS1 одржавање: Формат датума (веза)
scientificamerican.com
Andrewes, William J. H. (1. 2. 2006). „A Chronicle of Timekeeping: Our conception of time depends on the way we measure it”. Scientific American. Приступљено 1. 5. 2017. „As William J. H. Andrewes (2006) notes: "In 1675 Huygens devised his next major improvement, the spiral balance spring. (...) The spiral balance spring revolutionized the accuracy of watches, enabling them to keep time to within a minute a day. This advance sparked an almost immediate rise in the market for watches, which were now no longer typically worn on a chain around the neck but were carried in a pocket, a wholly new fashion in clothing."”CS1 одржавање: Формат датума (веза)
„A Revolution in Timekeeping, part 3”. A Walk Through Time. NIST (National Inst. of Standards and Technology). 2002. Архивирано из оригинала 28. 5. 2007. г. Приступљено 28. 5. 2014.CS1 одржавање: Формат датума (веза)
