Question: What is the alma mater of the scientists  known for  String theory?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri WHERE { ?x onto:knownFor <http://dbpedia.org/resource/String_theory> . ?x prop:almaMater ?uri  . ?x rdf:type onto:Scientist}