Question: What is the country whose leader was once Valentina Matviyenko?
SPARQL query: SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/ontology/leader> <http://dbpedia.org/resource/Valentina_Matviyenko>  . }
Answer: The country led by Valentina Matviyenko is [Russia, Federal Assembly (Russia), Federation Council (Russia)].