Younger, R. M.
Victoria Hutchinson Group 1982
Buku Teks
Goldschmidt, Arthur, author
Westview Press, 1983
Buku Teks
Burickson, Sherwin, author
Philosophical Library, 1959
Buku Referensi
Heidhues, Mary Somers
Thames dan Hudson , 2000
Buku Teks
Read, Herbert Edward, Sir, author
Praeger , 1959
Buku Teks