二百五十七角形
↑ Richelot, Friedrich Julius (1832). “De resolutione algebraica aequationis X = 1, sive de divisione circuli per bisectionem anguli septies repetitam in partes 257 inter se aequales commentatio coronata” (Latin). Journal für die reine und angewandte Mathematik 9: pp. 1–26, 146–161, 209–230, 337–358. http://www.digizeitschriften.de/resolveppn/PPN243919689_0009.
↑ Coxeter, H. S. M. (February 1989). Introduction to Geometry (2nd ed. ed.). New York: Wiley. ISBN 978-0-471-50458-0