Tham khảo Tam giác đều

  1. 1 2 3 De, Prithwijit, "Curious properties of the circumcircle and incircle of an equilateral triangle," Mathematical Spectrum 41(1), 2008-2009, 32-35.
  2. ↑ Posamentier, Alfred S., and Salkind, Charles T., Challenging Problems in Geometry, Dover Publ., 1996.
  3. ↑ Posamentier, Alfred S., and Salkind, Charles T., Challenging Problems in Geometry, second edition, Dover Publ. Co., 1996, pp. 170-172.