Ryan, Gig
Pan Books, 1990
Buku Teks
Williams, Alexander
Cambridge University Press, 2015
eBooks
Herrick, James A.
Pearson custom, 1998
Buku Teks SO
Mander, Jerry
Morrow Quill Paperbacks, 1978
Buku Teks SO
Muhammad Irvan
Sekolah Kajian Stratejik dan Global Universitas Indonesia, 2010
UI - Tesis Open