1. Acemoglu, D., & Robinson, J. A. (2019). The narrow corridor: States, societies, and the fate of liberty. London: Penguin Press.
2. Aghion, P., & Howitt, P. (1997). Endogenous growth theory. Cambridge: MIT Press.
3. Anderson, J. L. (1991). Explaining long-term economic change. London: Macmillian.
4. Asbridge, T. (2004). The first crusade: a new history. Oxford: Oxford University Press.
5. Bachrach, B. S. (1974). Military organization in Aquitaine under the early Carolingians. Speculum, 49(1), 1–33.