Gaspar, P.P., Reform, the New Technology and Tower Hill, Challis, C.E. (编), A New History oftheRoyalMint, Cambridge, UnitedKingdom: Cambridge University
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(原始内容存档于2018-08-28). Royal Mint – 20p coin(页面存档备份,存于互联网档案馆) Coins ofthe UK – Decimal 20p Coin(页面存档备份,存于互联网档案馆) Coins from UnitedKingdom: Twenty Pence | Online
(原始内容存档于2019-02-04). UnitedKingdom £1 Coin. RoyalMint. [2021-12-01]. (原始内容存档于2008-04-30). James Marr. The History of Guernsey: The Bailiwick's Story 2nd