John Wiley & Sons, 2010
eBooks
Shayne Cox Gad.
Wiley-Interscience , 2017
Buku Referensi
Bayt, Phyllis Theiss
Glencoe Publishing Company, 1982
Buku Teks SO
Ansel, Howard C., 1933-
Wolters Kluwer, 2017
Buku Teks SO
Allan, Barbara
Facet Publishing, 2004
Buku Teks SO