The Work Bank , 1981
Buku Teks
edited by John A. Wiseman
Routledge, 1995
Buku Teks SO
editor Peter de Haan and Yvonne van Hees
Netherlands Development Cooperation Information Department, 1996
Buku Teks SO
Nielsen, Waldemar A.
Atheneum, 1966
Buku Teks SO
Esacove, Anne
Oxford University Press, 2016
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