2020. สืบค้นเมื่อ 9 October 2019. MacLeary, John (12 February 2014). "Twentyquestions with ... former Olympic triple jump gold medallist and world record
และเขตสหพันธ์ไซบีเรีย Waters, Bella (1 September 2008). Armenia in Pictures. Twenty-First Century Books. p. 69. ISBN 9780822585763. สืบค้นเมื่อ 29 April 2017
107–9 and 113. On TwentyQuestions, p. 109, Peirce has pointed out that if each question eliminates half the possibilities, twentyquestions can choose from
ozonewatch.gsfc.nasa.gov. สืบค้นเมื่อ 2018-11-12. Fahey, David W. (2011). Twentyquestions and answers about the ozone layer 2010 update: scientific assessment