Doody, Francis S.
New York, N.Y. Random c.1965,
Buku Teks
Unesco Press, 1979
Buku Teks
Sullivan, John L. (John Lawrence), 1945-, author
Sage, 1979
Buku Teks SO
Stutely, Richard
Century Business, 1992
Buku Teks
Rummel, J. Francis
Harper & Row, 1964
Buku Teks