Field, John
Routledge, 2005
Buku Teks SO
edited by Michael Tomasello
Lawrence Erlbaum Associates, 2003
Buku Teks
Cambridge University Press, 1994
Buku Teks
Lambert, Wallace E.
Stanford University press, 1972
Buku Teks
edited by Howard Giles and W. Peter Robinson
John Wiley & Sons, 1990
Buku Referensi