consultant editor, D.E. Hathway
Harrap, 1985
Buku Referensi
Wichman, K., author
New York, David Mckay Company
Buku Referensi
English Universities Press, 1955
Buku Referensi
editor, Philip Babcock Gove
Merriam-Webster, 1993
Buku Referensi
Jones, Daniel
University Press, 1958
Buku Teks