@inproceedings{DBLP:conf/ecsqaru/BruningS99,
  author = {Br{\"{u}}ning, Stefan and Schaub, Torsten},
  title = {Avoiding Non-ground Variables},
  booktitle = {{ESCQARU}},
  series = {Lecture Notes in Computer Science},
  volume = {1638},
  pages = {92--103},
  publisher = {Springer},
  year = {1999}
}