@article{DBLP: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}
}