Classification of tight regular polyhedra
  A regular polyhedron of type {p, q} has at least 2pq flags, and it is called tight if it has exactly 2pq flags. The values of p and q for which there exist tight orientably regular polyhedra were previously known. We determine for which values of p and q there is a tight non-orientably regular polyhedron of type {p, q}. Furthermore, we completely classify tight regular polyhedra in terms of their automorphism groups. 
Gabe Cunningham and Daniel Pellicer
math.CO