A note on Gunningham's formula
  Gunningham [G] constructed an extended topological quantum field theory (TQFT) to obtain a closed formula for all spin Hurwitz numbers. In this note, we use the gluing theorem in [LP2] to re-prove the Gunningham's formula. We also describe a TQFT formalism naturally induced from the gluing theorem. 
Junho Lee
math.SG