Human geography : issues for 21st century
Peter Daniels [and others]
Prentice-Hall, 2001
 Buku Teks
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
Harrington, Rick
Stress, health and well-being: thriving in the 21st century
Wadsworth and Cengage Learning, 2013
 Buku Teks
Social issues in health care
edited by Donnie J. Self
Teagle & Little, 1977
 Buku Teks