query: #title: Check value
  # Complex constraint from [[Property talk:P220]]
  #
  SELECT ?item ?value ?marc {
  	?item wdt:P220 ?value.
    ?item wdt:P4801 ?marc.
    BIND (SUBSTR(?marc, 1, 9) AS ?prefix).
    BIND (SUBSTR(?marc, 11) AS ?s).
    FILTER (?marc = ?s)
  }