edited by Quentin H. Stanford
Oxford University Press, 1972
Buku Teks
edited by Mindel C. Sheps and Jeanne Clare Ridley
University of Pittsburgh Press, 1965
Buku Teks
Zito, George V., author
Human Science Press, 1979
Buku Teks
Artikel Jurnal
Berman, Donald H., author
Oceana Publication, 1972
Buku Teks