Crystal, David, 1941-
The Cambridge encyclopedia of language
Cambridge University Press, 1994
 Buku Referensi
Crystal, David, 1941-
The Cambridge encyclopedia of language
Cambridge University Press, 1991
 Buku Referensi
Crystal, David, 1941-
The Cambridge encyclopedia of language
Cambridge University Press, 1997
 Buku Referensi
Labov, William
Principles of linguistic change; volume 2: social factors
Blackwell, 2001
 Buku Teks
Crystal, David, 1941-
Ensiklopedi Bahasa = The Cambridge encyclopedia of language
Nuansa Cendekia, 2015
 Buku Referensi