APA (7th ed.) Citation

Gray, N. (1990). Activated sludge. Theory and practice (1a ed.). Oxford University Press.

Chicago Style (17th ed.) Citation

Gray, N.F. Activated Sludge. Theory and Practice. 1a ed. Oxford: Oxford University Press, 1990.

MLA (9th ed.) Citation

Gray, N.F. Activated Sludge. Theory and Practice. 1a ed. Oxford University Press, 1990.