APA (7th ed.) Citation

Mill, Gray, & Smith. (1991). J.S. Mill, On liberty, in focus. Routledge.

Chicago Style (17th ed.) Citation

Mill, Gray, and Smith. J.S. Mill, On Liberty, in Focus. London: Routledge, 1991.

MLA (9th ed.) Citation

Mill, et al. J.S. Mill, On Liberty, in Focus. Routledge, 1991.