You might look for scholarly theses or dissertations written by graduate students. These are usually available via interlibrary loan from the university where the student obtained his/her degree. Usually, academic libraries have books that list the titles of such research. Look up "Lynching" and don't limit yourself to Mississippi universities. Particularly look into graduate research done in New Orleans universities (UNO and Tulane). Check the historical journals such as the Journal of Louisiana History, and those published by other historical associations -- Southern Historical Review, etc. Good luck!