What is the label of the album whose previous work is Waterfall?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/previousWork> <http://dbpedia.org/resource/Waterfall_(album)> . ?x <http://dbpedia.org/property/label> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Album>}
Waterfall_(album)