@Article{SIGASIA08-Ritschel,
  author = {Tobias Ritschel and Thorsten Grosch and Min H. Kim and Hans-Peter Seidel and Carsten Dachsbacher and Jan Kautz },
  title  = {{Imperfect Shadow Maps for Efficient Computation of Indirect Illumination }},
  year   = {2008},
  journal = {ACM Transactions on Graphics (Proceedings of SIGGRAPH Asia 2008)},,
  number = {5},
  volume = {27}
}