Paris Pamfilos, On the Newton line of a quadrilateral,
Forum Geometricorum, 9 (2009) 81--98.

Abstract: We introduce the idea of the conjugate polygon of a point relative to another polygon and examine the closing property of polygons inscribed in others and having sides parallel to a conjugate polygon. Specializing for quadrangles we prove a characterization of their  Newton line related to the possibility to inscribe a quadrangle having its sides parallel to the sides of a conjugate one.

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