UNICEF
Unicef, 2002
Buku Teks
Jarvinen, Margaretha, author
Scandinavian University Press, 1993
Buku Teks
Ollenburger, Jane C., author
Rineka Cipta, 1996
Buku Teks
Powell, Gary N.
Sage Publications, 1988
Buku Teks
Adler, Freda, author
Houghton Mifflin, 1979
Buku Teks