@article{<a href="http://dblp.uni-trier.de/db/about/bibtex.html">DBLP</a>:journals/pvldb/BaranyCO12,
  author    = {Vince B{\'a}r{\'a}ny and
               Balder ten Cate and
               Martin Otto},
  title     = {Queries with Guarded Negation},
  journal   = {PVLDB},
  volume    = {5},
  number    = {11},
  year      = {2012},
  pages     = {1328-1339},
  ee        = {http://vldb.org/pvldb/vol5/p1328_vincebarany_vldb2012.pdf},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}