query: SELECT ?authorstring ?citedpaper 
  WHERE
  { 
    { ?paper wdt:P2860 ?citedpaper . } 
    { ?citedpaper wdt:P31 wd:Q13442814 . } 
    { ?citedpaper wdt:P50 ?author . } 
    { ?citedpaper wdt:P2093 ?authorstring . } 
  
  #  FILTER(CONTAINS(LCASE(?authorstring), "smith"))
  }
  GROUP BY ?authorstring ?citedpaper 
  