1. P. J. Cameron, D. R. Hughes, and A. Pasini, “Extended generalized quadrangles,” Geom. Dedicata,35, No. 1–3, 193–228 (1990)
2. E. E. Shult, “Groups, polar spaces and related structures,” Math. Centre Tracts., Amsterdam,57, 130–161 (1974)
3. F. Buekenhout and X. Hubaut, “Locally polar spaces and related rank 3 groups,” J. Algebra,45, No. 2, 391–434 (1977).
4. A. Blorhuis and A. E. Brouwer, “Locally 4-by-4 grid graphs,” J. Graph Theory,13, No. 2, 229–244 (1989)
5. S. E. Payne and G. A. Thas, Finite Generalized Quadrangles, Pitman, Boston (1884).