query: embed.html#SELECT DISTINCT ?paper ?label (SAMPLE(?subject) AS ?subject) WHERE {
    ?paper wdt:P31 wd:Q13442814.
    ?paper wdt:P50 ?author.
    ?author wdt:P108 / wdt:P17 wd:Q145 .
    ?paper rdfs:label ?label.
    FILTER(LANG(?label) = "en").
     FILTER REGEX(?label, "(Wales)") .
     OPTIONAL {
     ?paper wdt:P921 ?subject. }
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
    }
  GROUP BY ?paper ?label
  LIMIT 100
  