Shao-Cheng Liu, A Generalization of Th\'ebault's Theorem on  the Concurrency of Three Euler Lines,
Forum Geometricorum, 8 (2008) 205--208.

Abstract: We prove a generalization of Victor Th\'ebault's theorem that if H_aH_bH_c is the orthic triangle of ABC, then the Euler lines of triangles AH_cH_b, BH_aH_c, and CH_bH_a are concurrent at the center of the Jerabek hyperbola which is the isogonal tranform of the Euler line.

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