Was a paper not not co-authored by Xiaohan Helu and Haitao Sun?
Didn't Xiaohan Helu and Haitao Sun not co-author a paper?
ASK { ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/245/0993> . ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/83/206> }
<https://dblp.org/pid/245/0993> <https://dblp.org/pid/83/206>