Didn't H. C. Ratz and Giordano B. Ferreira not co-author a paper?
Was a paper not not co-authored by Ratz, H. C. and G. B. Ferreira?
ASK { ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/78/4801> . ?x <https://dblp.org/rdf/schema#authoredBy> <https://dblp.org/pid/43/8506> }
<https://dblp.org/pid/78/4801> <https://dblp.org/pid/43/8506>