Harrod, R.F., author
Macmillan, 1956
Buku Teks
Chamberlain, Neil W. (Neil Wolverton), author
Harper & Brothers , 1955
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Crabbe, Ernest H., author
South-Western Publishing, 1961
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Lawson, Robert W., author
University Paperbacks, 1952
Buku Teks
Candra Aji Kusuma, author
Research and Development Agency Ministry of Home Affairs, 2018
Artikel Jurnal