Flower, William Henry
Routledge/Thoemmes Press, 1996
Buku Referensi
Edwards, Edward
Routledge/Thoemmes Press, 1996
Buku Referensi
Lunden, Staffan
Goteborg Universitet, 2016
Buku Teks
Ambrose, Timothy
Routledge, 1995
Buku Teks
Woo, Kyu Sung
Rockport Publishers, 1999
Buku Teks SO