(1987). Walford's guide to reference material (4th ed.). Library Association.
Chicago Style aipamenaWalford's Guide to Reference Material. 4th ed. London: Library Association, 1987.
MLA aipamenaWalford's Guide to Reference Material. 4th ed. Library Association, 1987.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.