Plumb, John Harold, 1911-
Penguin Books, 1963
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Walsh, Linda
John Wiley & Sons, 2017
Buku Teks SO
Hill, Bridget
UCL Press, 1994
Buku Teks
Plumb, John Harold, 1911-
Penguin Books , 1951
Buku Teks SO
Brugge, CJM Lubbers-Van der
Groningen Wolters 1951
Buku Teks