Bach, George Leland, author
Prentice-Hall, 1956
Buku Teks
Walker, E. Ronald, author
University of Chicago Press, 1947
Buku Teks
Harrod, R.F., author
Macmillan, 1956
Buku Teks
Seth, M.L., author
S. Chand, 1969
Buku Teks
North, Douglass C.
Harper & Row, 1971
Buku Teks