Neumayer, Eric
Cambridge University Press, 2017
eBooks
Osborn, John F.
Blackwell, 1979
Buku Teks SO
Fisher, Ronald A.
Hafner Press, 1970
Buku Teks SO
Myers, Jerome L.
Routledge, 2010
Buku Teks SO
Merrill, Ray M.
Jones & Bartlett Learning, 2016
Buku Teks SO