References
- Belnap, Nuel, Michael Perloff, and Ming Xu 2001. Facing the Future: Agents and Choices in Our Indeterminist World, New York: Oxford University Press.
- Hughes, G.E. and M.J. Cresswell 1996. A New Introduction to Modal Logic, Abingdon: Routledge.
- Kuhn, Steven and Brian Weatherson 2017. Notes on Some Ideas in Lloyd Humberstone's Philosophical Applications of Modal Logic (manuscript).