Coxeter- Figure 1.5C
This is a combination of many elementary correspondences. The number of lines and points can be any amount, in this example we chose three. In the book, we use a sequence of lines and points occurring alternately: . We allow the sequence to begin with a point (omitting ) or to end with a line (omitting ) but we insist that adjacent members shall be nonincident and that alternate members shall be distinct. This arrangement of lines and points enables us to establish a transformation relation the range of points on to the pencil of lines through . This is called a projectivity.