Colston, Herbert L., author
Cambridge University Press, 2015
Buku Teks
Artikel Jurnal
edited by Howard Giles and W. Peter Robinson
John Wiley & Sons, 1990
Buku Referensi
Devito, Joseph A., author
Random House, 1970
Buku Teks
Lemke, J.L. (Jay L.), author
Oxford University Press, 1989
Buku Teks