Question: Which president of William Eustus also married to Dolley Madison ?
SPARQL query:
PREFIX res: <http://dbpedia.org/resource/>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
 SELECT DISTINCT ?uri WHERE { res:Dolley_Madison onto:spouse ?uri. res:William_Eustis prop:president ?uri}