Sommerlad, Elizabeth, author
Australian National University Press, 1976
Buku Teks
Haag, Stephen, author
McGraw-Hill, 1996
Buku Teks
Artikel Jurnal
Johnson, James Weldon, author
Viking , 1969
Buku Teks
Tanjung Akbar
Gramedia Pustaka Utama, 2007
Buku Teks