Bruce, Debra Fulghum
Macmillan General Reference, 1998
Buku Teks SO
Bruce, Debra Fulghum
Macmillan General Reference, 1998
Buku Teks SO
Fontaine, Karen Lee
Que, 2004
Buku Teks SO
Brockhampton Reference
Brockhampton Press, 1996
Buku Teks SO
Anderson, Robert A.
McGraw-Hill, 1991
Buku Teks SO