@article{GebserLeeLierler2011,
  author    = {Martin Gebser and Joohyung Lee and Yuliya Lierler},
  title     = {On elementary loops of logic programs},
  journal   = {Theory and practice of logic programming},
  volume    = {11},
  number    = {2},
  pages     = {953 -- 988},
  doi       = {10.1017/S1471068411000019},
  year      = {2011},
}