UNICEF
UNICEF, 1988
Buku Teks
Pelligrini, Anthony D., author
Lawrence Elbaum Associates, 1996
Buku Teks
Grant, P. James
Oxford University Press, 1986
Buku Teks
Russell, Richard Joel, author
Macmillan, 1954, 1951
Buku Teks
Russell, Richard Joel, author
Macmillan, 1958
Buku Teks