2020 vision health in the 21st century
National Academy Press, 1996
 Buku Teks
Friis, Robert H.
Occupational health and safety for the 21st century
Jones &​ Bartlett Learning, 2016
 Buku Teks
Health care ethics: critical issues for the 21st century
edited by Eileen E. Morrison, Beth Furlong
Jones & Bartlett Learning, 2014
 Buku Teks
Town planning into the 21st century
edited by Andrew Blowers, Bob Evans
Routledge, 1997
 Buku Teks
Ward, Ralph D.
21st century corporate board
John Wiley & Sons, 1997
 Buku Teks