1. Fong, P., Seitz, G.M.: Groups with a (B, N)-pair of rank 2, I and II. Invent. Math.21, 1?57 (1973) and24, 191?239 (1974)
2. Payne, S.E., Thas, J.A.: Finite generalized quadrangles. Pitman 1984
3. Tits, J.: Classification of buildings of spherical type and Moufang polygons: a survey. In: Segre, B. (ed.) Teorie Combinatorie. Roma Accad. Naz. Lincei 229?246 (1976)