"Cyclic number". The Internet Encyclopedia of Science. คลังข้อมูลเก่าเก็บจากแหล่งเดิมเมื่อ 2007-09-29.
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Ecker, Michael W. (March 1983). "The Alluring Lore of Cyclic Numbers". The Two-Year College Mathematics Journal. 14 (2): 105–109. doi:10.2307/3026586. JSTOR3026586.
Ecker, Michael W. (March 1983). "The Alluring Lore of Cyclic Numbers". The Two-Year College Mathematics Journal. 14 (2): 105–109. doi:10.2307/3026586. JSTOR3026586.