Three different names of a 15 - set of type (3, 6)₂ in PG(3, 3)

The type of a point and a characterization of the set of external points of a conic inPG(2,q),qodd

“…We present the topic in a readable fashion, with particular attention to showing how original ideas of mathematics arise naturally from considerations well known to elementary students. Those with a good knowledge of school geometry should find the article very helpful as a bridge between old and new ideas, see also [12], [13], [18], [19] and [20],…”