Obstructions of Connectivity 2 for Embedding Graphs into the Torus
  The complete set of minimal obstructions for embedding graphs into the torus is still not determined. In this paper, we present all obstructions for the torus of connectivity 2. Furthermore, we describe the building blocks of obstructions of connectivity 2 for any orientable surface. 
Bojan Mohar and Petr \v{S}koda
math.CO