Carter, April, author
Longman, 1993
Buku Teks
Forsythe, David P., 1941-, author
University of Nebraska Press, 1983
Buku Teks
UNICEF
Unicef, 2002
Buku Teks
Stokes, Windy, author
Poloty Press, 2005
Buku Teks
Mayer, Ann Elizabeth, author
Westview Press, 1995
Buku Teks