^ 1.01.1鄭寶鴻. 圖片香港貨幣. 三聯書店(香港)有限公司. 1 August 2012: 40. ISBN 978-962-04-3278-1(中文(香港)). 外國銀元(即貿易銀)於明朝時已開始流入中國。...由於中國人不喜歡洋貨,外國人不能用以物易物的方式交,只能用銀元來購買中國的絲、茶葉和瓷器等等。 當時的外國銀元有葡萄牙的十字銀元、日耳曼帝國的塔勒、荷蘭的馬劍幤、美國的五先令、美國的銀元以及西班牙的「本洋」等。
^ 2.02.12.2Larry Allen. The Encyclopedia of Money. ABC-CLIO. 2009: 70. ISBN 978-1-59884-251-7(英語). In 1895, the United Kingdom, itself on the gold standard, began issuing silver dollars, called "trade dollars," specifically for trade with the Far East. British trade dollars bore inscriptions in English, Chinese, and Malay-Arabic. Briefly during the latter 19th century, the United States issued a special trade dollar designed specifically to compete with the Mexican dollar in Far Eastern trade. The Chinese called these various silver dollars yuan, meaning "round things," and yuan became the standard monetary unit in China and modern Taiwan.