Mortimer, J.E.
Oxford University Press , 1971
Buku Teks
Clegg, H. A., author
Clarendon Press, 1964
Buku Teks
edited and compiled by Wolodymyr Maksymiw
Longman, 1990
Buku Referensi
McIlroy, John, author
Manchester University Press , 1995
Buku Teks
edited by Hilary Dyer and Gwyneth Tseng
Taylor Graham, 1988
Buku Teks