First we define relations between the v = (s2+s+1}(s+l) flags (point-line incident pairs) of a finite projective plane of order s. Two flags a =(p,i) and b =(p' ,l'), where p and p' are two points and l and l' are two lines of the projective plane, are defined to be first associates if either p = p' or l = l'; second associates if p # p', l # l' but either p is incident also with l' or p' is in...