to polygons with more than three sides. The centroid, for instance, can be found for any polygon. Some research has been done on the centers of polygons with more than three sides. See also Central line Encyclopedia of Triangle Centers Triangle conic Central triangle Modern triangle geometry Notes External links Manfred Evers, On Centers and Central Lines of Triangles in the Elliptic Plane Manfred Evers, On the geometry of a triangle in the elliptic and in the extended hyperbolic plane Clark Kimberling, Triangle Centers from University of Evansville Ed Pegg, Triangle Centers in the 2D, 3D, Spherical and Hyperbolic from Wolfram Research. Paul Yiu, A Tour of Triangle Geometry from Florida Atlantic University.