Neufeldt, Victoria, author
Prentice Hall ; Modern English Press, 1993
Buku Referensi
editor, Philip Babcock Gove
Merriam-Webster, 1993
Buku Referensi
daab, 2004
Buku Teks
Orme, John
Massaschusetts Massachusetts Institute of Technology 1997,
Buku Teks
Encyclopaedia Britannica, 1981
Buku Referensi