香港大学发现赵紫阳许诺民主治港信函 (University uncovers 1984 letter by late premier Zhao Ziyang voicing support for democracy in Hong Kong)
British Broadcasting Corporation, January 9, 2014
www.bbc.co.uk/zhongwen/simp/china/2014/01/140109_hongkong_zhao_ziyang_letter.shtml