Didn't Rif\u00E0, J. and Griera, Merc\u00E8 not co-author a paper?
Was a paper not not co-authored by Rif\u00E0, J. and Griera, Merc\u00E8?
ASK { ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/r/JosepRifa> . ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/91/3484> }
<https://dblp.org/pid/r/JosepRifa> <https://dblp.org/pid/91/3484>