@inproceedings{BSDSW04,
  author      = {Kevin Buchin and
                 Mario Costa Sousa and
                 J\"{u}rgen D\"{o}llner and
                 Faramarz Samavati and
                 Maike Walther},
  title       = {Illustrating Terrain Using Direction of Slope and Lighting},
  booktitle   = {Proceedings of the 4th ICA Mountain Cartography Workshop},
  location    = {Vall de N\'{u}ria, Spain},
  month       = {Sep 30-Oct 2}, 
  pages       = {259-269},
  year        = {2004}
}