query: SELECT ?item ?itemLabel ?doi
  WHERE
  {
    BIND ( "10.1023/A" as ?search_string )
    hint:Query hint:optimizer "None".  
    SERVICE wikibase:mwapi
    {
      bd:serviceParam wikibase:endpoint "www.wikidata.org" .
      bd:serviceParam wikibase:api "Generator" .
      bd:serviceParam mwapi:generator "search" .
      bd:serviceParam mwapi:gsrsearch ?search_string .
      bd:serviceParam mwapi:gsrlimit "max" .    
      bd:serviceParam mwapi:gsrnamespace "0" .    
      ?item wikibase:apiOutputItem mwapi:title  .
    }
    FILTER( BOUND(?item) )
    ?item wdt:P356 ?doi 
    FILTER ( CONTAINS(?doi, ?search_string) )
    FILTER NOT EXISTS { ?item wdt:P1476 [] }   
    OPTIONAL { ?item wdt:P31 ?instance_of }
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en" }
  }
  