Gass, William H
Harper & Row, 1968
Buku Teks
Gonda, J. (Jan), 1905-1991, author
North Holland Publishing, 1985
Buku Teks
Zwerman, William L
Greenwood Publishing Corporation, 1970
Buku Teks
Wicker, Tom
Times Book, 2002
Buku Teks
edited by Peter Trudgill and J.K. Chambers
Longman, 1991
Buku Teks