Bowers, Faubion, author
Thomas Nelson & Sons, 1956
Buku Teks
New York : Science Press
Majalah, Jurnal, Buletin
Elam, Keir, author
Methuen, 1980
Buku Teks
Cassady, Marshall, author
National Textbook, 1993
Buku Teks
editor, James R. Brandon
Cambridge Unipersity Press, 1993
Buku Referensi