then "H" is generated by the 3 involutions "a", "ab" and "ab"5. The link of each vertex is given by the corresponding Cayley graph, so is just the bipartite Heawood graph, i.e. exactly the same as in the affine building for "SL"3(Q2). This link structure implies that the corresponding simplicial complex is necessarily a Euclidean building. At present, however, it seems to be unknown whether any of these types of action can in fact be realised on a classical affine building: Mumford's group Γ1 (modulo scalars) is only simply transitive on edges, not on oriented edges.