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World population : challenges for the 21st century
Seven Lucks Press, 1999
Buku Teks
Southeast Asia : challenges of the 21st century / by Janadas Devan
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Buku Teks SO
"Challenges for the british library in the 21st century" Lynne Brindley
Artikel Jurnal
Energy, environment and sustainable development: Challenges for the 21st century
1993
Buku Teks SO
Nazrul Hoque, editor
Opportunities and challenges for applied demography in the 21st century
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