How to get all Abbasid rulers ordered chronologically in nomisma.org SPARQL endpoint

gistfile1.sparql

PREFIX rdf:	<http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX dcmitype:	<http://purl.org/dc/dcmitype/>
PREFIX dcterms:	<http://purl.org/dc/terms/>
PREFIX foaf:	<http://xmlns.com/foaf/0.1/>
PREFIX geo:	<http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX nm:	<http://nomisma.org/id/>
PREFIX nmo:	<http://nomisma.org/ontology#>
PREFIX org:	<http://www.w3.org/ns/org#>
PREFIX osgeo:	<http://data.ordnancesurvey.co.uk/ontology/geometry/>
PREFIX rdac:	<http://www.rdaregistry.info/Elements/c/>
PREFIX skos:	<http://www.w3.org/2004/02/skos/core#>
PREFIX spatial: <http://jena.apache.org/spatial#>
PREFIX un:	<http://www.owl-ontologies.com/Ontology1181490123.owl#>
PREFIX xsd:	<http://www.w3.org/2001/XMLSchema#>

SELECT ?s ?label ?startDate ?endDate WHERE {
?s a foaf:Person ;
     org:hasMembership ?membership .
  ?s skos:prefLabel ?label FILTER langMatches(lang(?label), "en") .
  ?membership org:organization nm:abbasids ;
              nmo:hasStartDate ?startDate ;
              nmo:hasEndDate ?endDate
} ORDER BY ?endDate