Logarithmic intertwining operators and the space of conformal blocks   over the projective line
  We show that the space of logarithmic intertwining operators among logarithmic modules for a vertex operator algebra is isomorphic to the space of 3-point conformal blocks over the projective line. This is considered as a generalization of Zhu's result for ordinary intertwining operators among ordinary modules. 
Yusuke Arike
math.QA