Nikolaos Dergiades and Juan Carlos Salazar, Some triangle
centers associated with the tritangent circles,
Forum Geometricorum, 9 (2009) 259--270.
Abstract: We investigate two interesting special
cases of the classical Apollonius problem, and then apply these to the tritangent
circles of a triangle to find pair of perspective (or homothetic) triangles.
Some new triangle centers are constructed.