Name the scientist whose doctoral supervisor's doctoral student is John Bowlby?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/doctoralStudent> <http://dbpedia.org/resource/John_Bowlby> . ?uri <http://dbpedia.org/property/doctoralAdvisor> ?x  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Scientist>}
John_Bowlby