what is the {stated as} for {Proceedings of the National Academy of Sciences of the United States of America} has {author} as {National Academy of Sciences} ?
Give the name of the author  in the National Academy of Sciences for Proceedings of the National Academy of Sciences of USA.
Who is the author in the National Academy of Sciences for Proceedings of the National Academy of Sciences of the United States of America?
SELECT ?d WHERE { ?e property:author resource:National_Academy_of_Sciences . ?e property:stated_as ?d . resource:Proceedings_of_the_National_Academy_of_Sciences_of_the_United_States_of_America property:author ?e }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1146531> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P50> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q270794> .
?statement <http://www.wikidata.org/entity/P1932> ?value. 
} 

SELECT ?value WHERE { wd:Q1146531 p:P50 ?s . ?s ps:P50 wd:Q270794 . ?s pq:P1932 ?value}