query: SELECT ?item ?release ?nr_s ?nr_e (GROUP_CONCAT(DISTINCT(?enlabel)) as ?enlabels) WHERE 
  {  
    ?item wdt:P31 wd:Q21191270 .
    ?item wdt:P179 wd:Q15106029 .   
    OPTIONAL {
       ?item wdt:P4908 ?season .
       ?season p:P179 ?season_statement .
       ?season_statement pq:P1545 ?nr_s  .
       ?item p:P4908 ?episode_statement .
       ?episode_statement pq:P1545 ?nr_e  .
    }
    OPTIONAL { ?item wdt:P577 ?release . }
    OPTIONAL { ?item rdfs:label ?enlabel . FILTER(lang(?enlabel)="en") }
  } GROUP BY ?item ?release ?nr_s ?nr_e ORDER BY xsd:integer(?nr_s) xsd:integer(?nr_e) ?release