APA (7th ed.) Citation

Open University. (1975). Files 1 ; [and], Files 2. Open University Press.

Chicago Style (17th ed.) Citation

Open University. Files 1 ; [and], Files 2. Milton Keynes: Open University Press, 1975.

MLA (8th ed.) Citation

Open University. Files 1 ; [and], Files 2. Open University Press, 1975.