edited by Gesina H.J. van der Molen, Willem Petrus Josef Pompe, J.H.W. Verzyl
Nederlandse Studentenvereniging, 1956
Buku Teks
New York : United Nations, 1968,
Buku Referensi
Departement of Public Information - United Nations, 1956
Buku Teks
UNESCO, 1951
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Coyle, David Cushman, 1887-1969, author
The New Americanan Library, 1962
Buku Teks