Cedric Jagger, Royal Clocks, The British Monarchy and its Timekeepers, 1300-1900, Hale, 1983, p. 277, figs. 378 & 379
Dr. Vaudrey Mercer, The Penningtons and their Balances, in Antiquarian Horology, Vol. XII, No. 5 (Spring 1981), pp. 514-522, illus.
Cedric Jagger, Paul Philip Barraud (with Supplement), concerning the Mudge copies
Thomas Mudge, junior, A Description with Plates of the Timekeeper invented by the late Thomas Mudge, 1799, facsimile by Turner & Devereux, 1977