Audas, James Wales
Whitcombe & Tombs, 1947
Buku Teks
Spencer, Baldwin, 1860-1929, author
Macmillan, 1899
Buku Teks
Frideres, James S.
Prentice Hall Canada, 1988
Buku Teks
Artikel Jurnal
Clark, C.M.H. (Charles Manning Hope), 1915-1991, author
Melbourne University Press, 1975
Buku Teks