Lambert, Wallace E.
Stanford University press, 1972
Buku Teks
edited by Howard Giles and W. Peter Robinson
John Wiley & Sons, 1990
Buku Referensi
Devito, Joseph A.
Random House, 1970
Buku Teks
Caplan, David
MIT Press, 1993
Buku Teks
Church, Joseph
Random House, 1961
Buku Teks