Merchant, John
Routledge, 2012
Buku Teks SO
edited by Roberto Walter Dal Negro and Richard Hodder
Springer, 2012
eBooks
Riley E. Dunlap ... et all, editor
Rowman & Littlefield Publishers, INC, 2001
Buku Teks SO
editors, Olen Gunnlaugson, Charles Baron, Mario Cayer
Igi Global, 2014
Buku Teks SO
Blake, Robert R.
Gulf Pub. Co., Book Division, 1978
Buku Teks