Campbell, James, author
University of Illinois Press, 1992
Buku Teks
United Nations Bureau of Social Affairs , 1955
Buku Teks
Phillips, D.C., author
Stanford University Press, 1976
Buku Teks
Go, Julian, author
Oxford University Press, 2016
eBooks
Knight, Peter T., author
Sage, 2002
Buku Teks