[1] E. GLOCK: Polaritäten von endlich erzeugten freien Ebenen. Math. Z. 110, 1969, (257-296). MR 0248625 | Zbl 0175.47702

[2] V. HAVEL: Incidence presystems. Mat. Čas. 20, 1970, (166-171). MR 0305230 | Zbl 0205.50102

[3] R. MAGAPI: Su certe structture algebriche associate ai piani graffi at to [?]. Boll. Unione Mat. Ital. 18, 1963, (238-251). MR 0160151

[4] O. PICKERT: Projektive Ebenen. Berlin-Göttingen-Heidelberg 1955. Zbl 0066.38707

[5] J. ANDRÉ: On generalized incidonco structures.

[6] J. ANDRÉ: On flats and dual-flats in incidence structures. Atti del Convegno di geometria combinatoria e sue applicazioni, Ist. Mat., Univ. Perugia, Perugia, 1971. MR 0340122

[7] R. H. F. DENISTON: Note on Devide's plane pre-projective geometries. Glasnik mat. 22, 1967, (163-166).

[8] V. DEVIDE: Plane pre-projective geometries. Glasnik mat. 20, 1965, 251-260 MR 0212663 | Zbl 0144.19603

[9] V. DEVIDE: Pre-geometric relations. Glasnik mat. 24, 1969, 243-253. MR 0256247 | Zbl 0207.19501

[10] V. HAVEL: Projective and affine preplanes. Glasnik mat. 23, 1968, 257-264. MR 0238175 | Zbl 0164.20702

[11] V. HAVEL: Zerlegungen von Inzidenzstrukturen 1. Publ. Math Debrecen 13, 1966, 99-103. MR 0205131

[12] V. HAVEL: Free extensions of coupled systems. Arch. math. Brno 3, 1967, 65-68. MR 0222760 | Zbl 0205.24403

[13] J. NALBACH: 68: Verbandstheoretische Charakterisierung regulären Pick $n$-ch i Inzidenzstrukturen. Diplomarbeit, Saarbrücken.