^Crilly, Tony (2007). 50 Mathematical Ideas You Really Need to Know. London: Quercus. p. 32. ISBN 978-1-84724-008-8.
^An account kept during thirteen months in the Royal Observatory at Greenwich of the going of a pocket chronometer made on a new construction by John Arnold. London. 1780.
^"chronometer, n.". Oxford English Dictionary online version (2nd ed.). 1989. Retrieved 2012-03-09. (subscription or participating institution membership required)
^"Copley Medal | British scientific award". Encyclopedia Britannica. Retrieved 21 July 2020.