Who was the president at the time when both Carl Stokes and Joseph Stiglitz held a position in US political framework?
SELECT DISTINCT ?uri WHERE { <http://dbpedia.org/resource/Carl_Stokes> <http://dbpedia.org/property/president> ?uri. <http://dbpedia.org/resource/Joseph_Stiglitz> <http://dbpedia.org/property/president> ?uri . }
Carl_Stokes Joseph_Stiglitz