Ambrose, Timothy
Routledge, 1995
Buku Teks SO
Woo, Kyu Sung
Rockport Publishers, 1999
Buku Teks SO
Abd. Salam
Fakultas Ilmu Pengetahuan Budaya Universitas Indonesia, 2010
UI - Tesis Open
Edwards, Edward
Thoemmes Press, 1996
Buku Referensi
Miguel Galas, 1970
Buku Teks SO