@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} }