Holtmaat, R.
H.D. Tjeenk Willink, 1989
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Banning, W.
Den Haag Servire's Encyclopaedie 1949,
Buku Teks
Kramer, W.
J.B. Wolters, 1947
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Duffus, R.L
Alfred A. Knopf, 1928
Buku Teks
Kirk, Franklyn W.
American Technical Society, 1975
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