PREFIX dgp353:  <http://data-gov.tw.rpi.edu/vocab/p/353/>
prefix foaf:  <http://xmlns.com/foaf/0.1/> 
PREFIX dgtwc:  <http://data-gov.tw.rpi.edu/2009/data-gov-twc.rdf#>
SELECT ?state_name ?state_population ?number_of_books as ?total_books 
WHERE {
    GRAPH <http://data-gov.tw.rpi.edu/vocab/Dataset_353>
    {  
         ?entry dgp353:phys_st ?state_code.
         ?entry dgp353:bkservol ?number_of_books.
         ?entry dgp353:popu_st ?state_population
    }
    GRAPH <http://data-gov.tw.rpi.edu/wikidata/United_States_and_Territories>
	{
	     ?s3  foaf:name  ?state_name .
	     ?s3  dgtwc:abbreviation ?state_code
	}    
}