Hutton, Clayton, author
M. Parrish, 1960
Buku Teks
Regional Office for South-East Asia, 1989
Buku Teks
Thiesmeyer, Lincoln R.
Little, Brown and Company, 1947
Buku Teks
Robertson, John
William Heinemann, 1981
Buku Teks
Crum, Leonard William
National Bureau of Economic Research , 1942
Buku Teks