Was a paper not not co-authored by J\u00E1n P. and John Simpson?
Didn't J\u00E1n P. and Simpson, John not co-author a paper?
ASK { ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/56/2142> . ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/222/1090> }
<https://dblp.org/pid/56/2142> <https://dblp.org/pid/222/1090>