Hart, J.M.
Allen& Unwin , 1951
Koleksi Publik
Jones, Bill, author
Manchester University Press, 1993
Buku Teks
Burrows, Toby, author
The Howorth, 1989
Buku Teks
edited by Raoul P. Colinvaux
Stevens, 1975
Buku Teks
Allen, G.C., author
Longman, Green, 1952
Buku Teks