Artikel Jurnal
Andre M N Renzaho
Imperial College Press, 2016
Buku Teks
edited by Peter C. Smith, Laura Ginnelly and Mark Sculpher
Open University Press, 2005
Buku Teks
Evi Fitriani, author
2017
Artikel Jurnal
Yong, H.E. Ong Keng, author
2006
Artikel Jurnal