Robinson, Joan, author
Macmillan, 1948
Buku Teks
Triffin, Robert, author
Harvard University Press, 1941
Buku Teks
Chamberlin, Edward Hastings, author
Harvard University Press, 1946
Buku Teks
Phlips, Louis, author
Cambridge University Press, 1988
Buku Teks
Chamberlein, Edward H., author
Macmillan, 1954
Buku Teks