“…A major result on finite generalized polygons is due to Feit & Higman [6] and states that for a finite generalized n-gon, n ≥ 3, of order (s, t), we always have either n = 3 (and then s = t), or n = 4 (and then s + t divides st(1 + st)), or n = 6 (and then st is a perfect square), or n = 8 (and then 2st is a perfect square), or n = 12 (and then 1 ∈ {s, t}). Each generalized n-gon S = (P, L, I) of order (s, s) gives rise to a unique generalized 2n-gon 2S = (P ∪ L, E) of order (1, s), called the double of S, where E is the set of flags of S (and a flag is an incident point-line pair).…”