Maria Flavia Mammana, Biagio Micale, and Mario Pennisi, On
the centroids of polygons and polyhedra,
Forum Geometricorum, 8 (2008) 121--130.
Abstract: In this paper we introduce the centroid of any finite set of points
of the space and we find some general properties of centroids. These properties
are then applied to different types of polygons and polyhedra.