Schickedanz, Judith A
Little, Brown & Co., 1982
Buku Teks
Smith, Peter K., author
Wiley, 2011
Buku Teks
Singer, Hans W. (Hans Wolfgang), author
United Nations, 1972
Buku Teks
Cobb, Nancy J., author
Mayfield Publishing Company , 2001
Buku Teks
Santrock, John W., author
McGraw-Hill, 2000
Buku Teks