(tiếng Anh)

• Encyclopedia of Triangles Centers by Clark Kimberling. The nine-point center is indexed as X(5), the Feuerbach point, as X(11), the center of the Kiepert hyperbola as X(115), and the center of the Jerabek hyperbola as X(125).
• Nine Point Center by Antonio Gutierrez from Geometry Step by Step from the Land of the Incas.
• History about the nine-point circle based on J.S. MacCay's article from 1892: History of the Nine Point Circle
• Nine Point Circle in Java at Cut-The-Knot
• Feuerbach's Theorem: a Proof at Cut-The-Knot
• Special lines and circles in a triangle (requires Java)
• An interactive Java applet showing several triangle centers that lies on the Nine Point Circle.