James, L. Douglas (Leonard Douglas)
McGraw-Hill, 1971
Buku Teks SO
Goodman, Alvin S.
Prentice-Hall, 1984
Buku Teks SO
Grigg, Neil S.
McGraw-Hill, 1985
Buku Teks SO
Kuiper, Edward
Butterworth, 1967
Buku Teks SO
Washington The World Bank 1993,
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