Question: What are the other key people of the non-profit organisations whose one of the  key person is Joe Green ?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/keyPeople> <http://dbpedia.org/resource/Joe_Green_(entrepreneur)> . ?x <http://dbpedia.org/property/keyPeople> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Non-ProfitOrganisation>}