Owen, Wilfred, author
The Brookings Institution, 1972
Buku Teks
Carrol, John M.
E.P. Dutton & Co., Inc., 1964
Buku Teks
Marshall, Leon Carroll
Chicago, Ill, The University of Chicago Press
Buku Teks
Carroll, Phil
McGraw-Hill, 1954
Buku Teks
Nankivell, Owen
Avebury, 19965
Buku Teks