@MISC\{IMM2003-01426,
    author       = "B. D. Larsen and N. J. Christensen",
    title        = "Optimizing Photon Mapping Using Multiple Photon Maps for Irradiance Estimates",
    year         = "2003",
    month        = "feb",
    keywords     = "Photon mapping, Global Illumination, kd-tree",
    publisher    = "",
    address      = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/1426-full.html"
}