Ehrlich, J. W., author
Oceana Publications, 1962
Buku Teks
Walker, J.B.R.
Macmilland,, 1948
Buku Teks
James, King, author
Thomas Nelson and Sons, 1952
Buku Teks
W.M. Collins Son, 1971
Buku Teks
Stevenson, Burton, author
New York, Harper & Brothers
Buku Referensi