What is the {river} for {tributary} of {Hertfordshire}
What river is a tribute to Hertfordshire?
What river is a tributary for the Hertfordshire?
SELECT DISTINCT ?q WHERE { resource:Hertfordshire property:tributary ?q . ?q rdf:type ontology:river }
select distinct ?obj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q3410> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P974> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj . ?obj <http://www.wikidata.org/entity/P31> <http://wikidata.dbpedia.org/resource/Q4022> } 
 select distinct ?obj where { wd:Q3410 wdt:P974 ?obj . ?obj wdt:P31 wd:Q4022 } 