Walford, A. J., Day, A., Harvey, J. M., & Mullay, M. (1990). Walford's guide to reference material (5th ed.). Library Association.
Cita Chicago (17th ed.)Walford, Albert John, Alan Day, Joan M. Harvey, i Marilyn Mullay. Walford's Guide to Reference Material. 5th ed. London: Library Association, 1990.
Cita MLA (9th ed.)Walford, Albert John, et al. Walford's Guide to Reference Material. 5th ed. Library Association, 1990.
Atenció: Aquestes cites poden no estar 100% correctes.