query: # Email address P968 
  # email is optional 
  # Can have multiple values 
  # Must start with 'mailto:' and contain a '@' and end with a '.tld'
  
  SELECT DISTINCT 
  ?item ?itemLabel 
  ?email #Email address P968 
  ?emailPart1 ?emailPart2 ?emailPart3 #?emailPart4 ?emailPart4Length
  ?emailRefURL ?emailRefDate ?OffWebsiteP856
  
  WHERE 
  {
    ?item (p:P31/ps:P31) wd:Q28564,wd:Q11396180;wdt:P17 wd:Q55. 
    OPTIONAL {?item p:P968 [ps:P968 ?email].} # Email address P968  
      
    BIND(STRBEFORE(STR(?email), ":") as ?emailPart1)
    BIND(STRAFTER(STR(?email), ":") as ?emailPart2)
    BIND(STRAFTER(STR(?emailPart2), "@") as ?emailPart3)
  
    OPTIONAL {?item p:P856 [ps:P856 ?OffWebsiteP856].} #official website (P856)
    OPTIONAL {?item p:P968 [prov:wasDerivedFrom [pr:P854 ?emailRefURL]] .} #reference --> Reference url P854
    OPTIONAL {?item p:P968 [prov:wasDerivedFrom [pr:P813 ?emailRefDate ]] .} #reference --> Retrieved P813
    
    SERVICE wikibase:label { bd:serviceParam wikibase:language "nl". }
  
  }
  ORDER BY ASC(?emailPart3)
  
  