Ford, Thomas R.
Prentice-Hall, 1970
Buku Teks
edited by D.V. Glass and D.E.C. Eversley
E. Arnold, 1965
Buku Teks
Weeks, John R. (John Robert), 1944-
Cengage Learning, 2016
Buku Teks
Gulati, P.
Tata McGraw-Hill, 1984
Buku Teks
United Nations, 1983
Buku Teks