"Our Work". www.thelugarcenter.org. Retrieved April 7, 2019.
The Bipartisan Index ranks members of the United States Congress by their degree of bipartisanship (by measuring the frequency each member's bills attract co-sponsors from the opposite party and each member's co-sponsorship of bills by members of the opposite party). "Our Work: Bipartisan Index". The Lugar Center. Retrieved September 20, 2017.
The Lugar Center - McCourt School Bipartisan Index(PDF), The Lugar Center, March 7, 2016, retrieved April 30, 2017