@article{Clarberg2008a,
  author = {Petrik Clarberg and Tomas Akenine-M\"oller},
  title = "{Practical Product Importance Sampling for Direct Illumination}",
  journal = {Computer Graphics Forum (Proceedings of Eurographics 2008)},
  volume = {27},
  number = {2},
  year = {2008},
  pages = {681--690},
}