Herring, E. Pendleton
McGraw-Hill, 1936
Buku Teks
Schultze, Charles L.
The Brookings Institution, 1977
Buku Teks SO
Ehrenberg, Ronald G.
Pearsons Addison-Wesley , 2009
Buku Teks SO
Roberts, Harold S.
University of Hawaii Press, 1970
Buku Teks SO
Roberts, Harold S.
University of Hawaii Press, 1970
Buku Teks SO