Urquhart, Brian, author
Uppsala Dag Hammarskjold Foundation, 1996
Buku Teks
Oceana Publications, 1957
Buku Teks
Washington U.S. Department of Health, Education, and Welfare 1955
Buku Teks
Boulder Westview Press 1988,
Buku Teks
Johnson, Edgar N., author
Cornell University Press, 1950
Buku Teks