@article{7067,
      author       = "Sievers, Jörn and XIII. Congress of the International
                      Society for Photogrammetry, Helsinki, 1976. Commission I",
      title        = "Directional Reflectances of Terrain Objects from B & W
                      - Aerial Photos  ",
      year         = "1976",
      note         = "1 sv.",
}