query: # references with only “quote” but no other claims
  SELECT ?statement ?reference ?quote
  WITH {
    SELECT ?reference WHERE {
      ?statement prov:wasDerivedFrom ?reference.
      ?reference pr:P1683 ?quote;
                 ?pr [].
    }
    GROUP BY ?reference
    HAVING(COUNT(DISTINCT ?pr) = 1)
  } AS %references
  WHERE {
    INCLUDE %references.
    ?statement prov:wasDerivedFrom ?reference.
    ?reference pr:P1683 ?quote.
  }