Burton, William C., author
New York : Macmillan, 1992,
Buku Referensi
Bloomsbury Publishing Limited, 1993
Buku Referensi
Burren, J.W., author
Clarendon Press , 1989
Buku Teks
Burren, J.W., author
Clarendon Press , 1989
Buku Teks
Oneworld , 2000
Buku Teks