Denning, Sir Alfred
Stevens & Sons Limited, 1955
Buku Teks
Sachs, Albie
University of California Press, 1973
Buku Teks
Kunstler, William M.
Oceana Publications, Inc, 1963
Buku Teks
Lassee, Isabelle, author
Cambridge University Press , 2017
Artikel Jurnal
Pound, Roscoe, author
Yale University Press, 1952
Buku Teks