how effective is President Obama negotiation skills in regard to U.S. relations with Iran
One place to start are the EBSCO databases.
On the Find Articles page of the Online Library, you should see near the top a link for "Search All EBSCO databases."
You could type one word in each search box: Obama in the first box; Iran in the second row; negotiation in the third row then click the search button.
There are hundreds of articles in the EBSCO databases that somehow discuss this topic.