Bouvier, Leon F.
World population : challenges for the 21st century
Seven Lucks Press, 1999
Buku Teks
Energy, environment and sustainable development: Challenges for the 21st century
1993
Buku Teks
Nazrul Hoque, editor
Opportunities and challenges for applied demography in the 21st century
[, Springer-Science], 2012
eBooks
Southeast Asia : challenges of the 21st century / by Janadas Devan
Institute of Southeast Asia Studies , 1994
Buku Teks
"Challenges for the british library in the 21st century" Lynne Brindley
Artikel Jurnal