APA (7th ed.) Citation

Pratchett, T. (2013). Guards! Guards!: A novel of Discworld. Harper.

Chicago Style (17th ed.) Citation

Pratchett, Terry. Guards! Guards!: A Novel of Discworld. New York: Harper, 2013.

MLA (9th ed.) Citation

Pratchett, Terry. Guards! Guards!: A Novel of Discworld. Harper, 2013.