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.

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