Artikel Jurnal
Wood, John, 1964 January 29- , author
Viking, 2013
Buku Teks
Engwicht, David
New Society Publihers, 1999
Buku Teks
Gilbert, Glen G., author
Jones and Burtlet, 2011
Buku Teks
Lambert, Joe, author
Routledge, Taylor & Francis Group, 2018
Buku Teks