Vishakha Wijenayake
Cambridge University Press , 2017
Artikel Jurnal
Denning, Sir Alfred
Stevens & Sons Limited, 1955
Buku Teks SO
Kunstler, William M.
Oceana Publications, Inc, 1963
Buku Teks SO
Pound, Roscoe
Yale University Press, 1952
Buku Teks SO
edited by Malcolm W. Klein
Sage, 1976
Buku Teks SO