Cambridge University Press, 1982
eBooks
Moody, William Vaughn
Charles Scribner's Sons, 1943
Buku Teks
Mulgan, John, author
Clarendon Press, 1967
Buku Teks
Mayhead, Robin
Cambridge University Press, 1974
Koleksi Publik
Wilson, John B., author
Longmans Green , 1958
Buku Teks