@article{DBLP:journals/tplp/GebserLL11,
  author = {Gebser, Martin and Lee, Joohyung and Lierler, Yuliya},
  title = {On elementary loops of logic programs},
  journal = {{TPLP}},
  volume = {11},
  number = {6},
  pages = {953--988},
  year = {2011}
}