Statistics for the twenty-first century
edited by Florence S. Gordon and Sheldon Gordon
Mathematical Association of America, 1992
 Buku Teks SO
Russel, Fox Hon
Justice in the twenty-first century
Covendish Publishing Limited, 2000
 Buku Teks
Twenty-first century: prospects and problems
edited by Kee Hyong Kim
Kyung Hee University Press, 1980
 Buku Teks SO
Capitalisms and capitalism in twenty-first century
edited by Glenn Morgan, Richard Whitley
Oxford University Press, 2012
 Buku Teks SO
Tax policy in the twenty-first century
edited by Herbert Stein
John Wiley & Sons, 1988
 Buku Teks SO