Fearnside, W. Ward
Prentice-Hall, 1997
Buku Teks SO
Antonietti, Alessandro, editor
Cambridge University Press, 2014
Buku Teks
Chesters, Sarah Davey
Sense, 2012
eBooks
James Piscatori
UIII Press, 2022
Artikel Jurnal
edited by Jessie Ee
McGraw-Hill, 2004
Buku Teks