2011]. (原始内容存档于2009-11-11). The following table gives specifications for TheUnitedStates Mint legal tender coins presently in circulation 请检查|date=中的日期值
(PDF)于2016-06-03). McGreevy, Thomas. Cunningham, Peter , 编. The Basis of Measurement: Volume 2 – Metrication and Current Practice. Pitcon Publishing (Chippenham)