List the birthplace of the medicians who studied in Harvard.
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/institution> <http://dbpedia.org/resource/Harvard_Medical_School> . ?x <http://dbpedia.org/ontology/birthPlace> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Medician>}
Harvard_Medical_School