signature." Cooper, David. The Petrie Collection of the Ancient Music of Ireland. Cork: Cork University Press, 2005. p. 22. "In a few cases Petrie has given what
與圓周率的計算無直接關係的事件會以淺紅色背景表示,世界紀錄會以淺青色背景表示,在表述圓周率的近似值小數以及其計算正確位數時無特別說明皆為用十進制。 Petrie, W.M.F. Surveys of the Great Pyramids. Nature Journal: 942-943. 1925 Arndt
Britannica Company. 1922. Sir Charles Petrie. The Chamberlain Tradition. London: Lovat Dickson Limited. 1938. Petrie, Sir Charles. The Life and Letters