Kunstler, William M.
Oceana Publications, Inc, 1963
Buku Teks SO
Lassee, Isabelle
Cambridge University Press , 2017
Artikel Jurnal
Pound, Roscoe
Yale University Press, 1952
Buku Teks SO
edited by Malcolm W. Klein
Sage, 1976
Buku Teks SO
Denning, Sir Alfred
Stevens and Sons Limited, 1949
Buku Teks