Please see google classroom for all the materials needed for your dissertation.
Below I've give you some links to help with your research.
Use your Farmer and McPherson book to begin with.
Preview of Hugh Tulloch, The Debate on the American Civil War
www.amazon.co.uk/Debate-American-Civil-Issues-Historiography/dp/0719049385
Interview with James McPherson
www.historynet.com/interview-with-civil-war-historian-james-mcpherson.htm