Name the river with Readin, Brekshire in its path and mouth place is Sothend-on-sea ?
SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/property/city> <http://dbpedia.org/resource/Reading,_Berkshire> . ?uri <http://dbpedia.org/ontology/mouthPlace> <http://dbpedia.org/resource/Southend-on-Sea>  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}
Reading,_Berkshire Southend-on-Sea