Was a paper not not co-authored by Kai H\u00F6ffner and Paul I. Barton?
Didn't H\u00F6ffner, Kai and Paul I. Barton not co-author a paper?
ASK { ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/157/1741> . ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/81/3426> }
<https://dblp.org/pid/157/1741> <https://dblp.org/pid/81/3426>