Polygons – Heptagons. coolmath.com. [2016-08-28]. (原始内容存档于2016-08-28). Gleason, Andrew Mattei. Angle trisection, the heptagon, and the triskaidecagon p. 186
ISBN 9781437707557. Strachan, Tom; Read, Andrew. Human molecular genetics 4th. New York: Garland Science. 2011. ISBN 9780815341499. Gleason, H. William; Taeusch, Roberta