> 51-XX Geometry > 51DXX Geometric closure systems

51D05 Abstract (Maeda) geometries	51D10 Abstract geometries with exchange axiom	51D15 Abstract geometries with parallelism
51D20 Combinatorial geometries	51D25 Lattices of subspaces	51D30 Continuous geometries and related topics
51D99 None of the above, but in this section

51DXX Geometric closure systems