Suarez, Thomas
Periplus, 1999
Buku Referensi
Routledge, 2018
Buku Teks SO
Greenhood, David
The University of Chicago Press, 1964
Buku Teks SO
Crampton, Jeremy W.
Wiley-Blackwell, 2010
Buku Teks SO
edited by Ronald I. Miller
Chapman & Hall, 1994
Buku Teks