Niederst, Jennifer
O`Reilly, 2001
Buku Referensi
Lawrence Erlbaum Associates, Publishers, 2005
Buku Teks
Boyle, Cailin
Rockport Publishers, 2001
Buku Teks
Frederick S. Merritt and Jonathan T. Ricketts, editor
McGraw-Hill, Inc, 1994
Buku Referensi
edited by W.A. Paton
Ronald Press, 1955
Buku Teks