Elbasha, Elamin H.
Minneapolis Economic Development Center Departement of Economics 1995,
Buku Teks
Free Press, 1979
Buku Teks
de Vries, Virginia H., author
Bureau of Printing, 1967
Buku Teks
Artikel Jurnal
Lucas, A.M.
Australia International Press , 1979
Buku Teks