Bhagwati, Jagdish
Penguin Books, 1969
Buku Teks
Houtte, Hans van
Sweet and Maxwell, 1995
Buku Referensi
Folsom, Ralph Haughwout
[Publisher not identified], [Date of publication not identified]
Buku Teks
Horn, Paul V.
Prentice-Hall, 1959
Buku Teks
Houtte, Hans van
Sweet and Maxwell, 1995
Buku Teks