@article{228,
      author       = "Hein, Günter and Landau, Herbert",
      title        = "A Contribution to 3D - Operational Geodesy. Part 3. OPERA -
                      A Multi-Purpose Program for Operational Adjustement of
                      Geodetic Observations of Terrestrial Type  ",
      year         = "1983",
      note         = "Liter., 1 sv.",
}