Studium na temat woli walki na poziomie narodowym: McNerney, Michael J., Ben Connable, S. Rebecca Zimmerman, Natasha Lander, Marek N. Posard, Jasen J. Castillo, Dan Madden, Ilana Blum, Aaron Frank, Benjamin J. Fernandes, In Hyo Seol, Christopher Paul, and Andrew Parasiliti, National Will to Fight: Why Some States Keep Fighting and Others Don’t. Santa Monica, CA: RAND Corporation, 2018.