@article{onthesatisfiabilityproblemforsparql,
  title = {On the satisfiability problem for SPARQL patterns},
  author = {Xiaowang Zhang and Jan Van den Bussche and François Picalausa},
  year = {2014},
  eprint = {1406.1404},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1406.1404v2},
}