Which rivers start in a country whose leader is Irene Mambilima?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/leaderName> <http://dbpedia.org/resource/Irene_Mambilima> . ?uri <http://dbpedia.org/ontology/sourceCountry> ?x  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}
Irene_Mambilima