APA (7th ed.) Citation

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

Chicago Style (17th ed.) Citation

Mill, John Stuart, G.W Smith, and John Gray. On Liberty in Focus. London: Routledge, 1991.

MLA (8th ed.) Citation

Mill, John Stuart, et al. On Liberty in Focus. Routledge, 1991.