Combinatorial Tilings of the Sphere by Pentagons
  A combinatorial tiling of the sphere is naturally given by an embedded graph. We study the case that each tile has exactly five edges, with the ultimate goal of classifying combinatorial tilings of the sphere by geometrically congruent pentagons. We show that the tiling cannot have only one vertex of degree >3. Moreover, we construct earth map tilings, which give classifications under the condition that vertices of degree >3 are at least of distance 4 apart, or under the condition that there are exactly two vertices of degree >3. 
Min Yan
math.CO