Acute Sets in Euclidean Spaces
If the five 3D coordinates 003 044 330 404 443 are plotted, all angles in all triangles are acute, so this is an example of an acute set. It was shown recently that nine points could form an acute set in four dimensions [1–3].
 D. Zakharov, "Acute Sets." arxiv.org/abs/1707.04829.
 B. Gerencsér and V. Harangi, "Acute Sets of Exponentially Optimal Size." arxiv.org/abs/1709.03411.
 Ed Pegg Jr. "Tight Acute Sets." Mathematics Stack Exchange. (Jan 9, 2018) math.stackexchange.com/questions/2363546/tight-acute-sets.