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.