Kimberling, Clark (1994), «Central Points and Central Lines in the Plane of a Triangle», Mathematics Magazine67 (3): 163-187, JSTOR2690608, MR1573021..
Kimberling, Clark (1994), «Central Points and Central Lines in the Plane of a Triangle», Mathematics Magazine67 (3): 163-187, JSTOR2690608, MR1573021..
Casey, J. (1866), «On the Equations and Properties: (1) of the System of Circles Touching Three Circles in a Plane; (2) of the System of Spheres Touching Four Spheres in Space; (3) of the System of Circles Touching Three Circles on a Sphere; (4) of the System of Conics Inscribed to a Conic, and Touching Three Inscribed Conics in a Plane», Proceedings of the Royal Irish Academy9: 396-423, JSTOR20488927.. See in particular the bottom of p. 411.