Mowaffaq Hajja and Margarita Spirova, A characterization of
the centroid using June Lester's shape function,
Forum Geometricorum, 6 (2006) 53--55.
Abstract: The notion of triangle shape is used to give another proof of
the fact that if P is a point inside triangle ABC and if the cevian
triangle of P is similar to ABC in the natural order, then P is the centroid.
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