Principles – In Motivational Pictures. [2011-09-16]. (原始内容存档于2011-09-12) (英语). Christy, Howard Chandler, The complete works of James Whitcomb Riley, 1982 鸭子类型
International Orienteering Federation. [2016-10-12]. (原始内容存档于2018-08-26). Christy O'Brien. The World Orienteering Championships in Scotland!. The Scots Magazine(英语:The