Schmeckebier, Laurence F., author
The Brookings Institution , 1961
Buku Teks
Frankel, Elana., author
Rockport Publishers, 2001
Buku Teks
J. Anthony Bristow, editor
John Wiley & Sons, 1997
Buku Referensi
Engdahl, David A., author
Chilton Books, 1967
Buku Teks
Osborner, David, author
Pustaka Binaman Pressindo, 1996
Buku Teks