Gardner, Richard K.
McGraw-Hill, 1981
Buku Teks
Artikel Jurnal
Merryman, John Henry
Stanford University Press, 1969
Buku Teks
Merryman, John Henry
Stanford University Press, 1985
Buku Teks
Maddison, Angus
New York, N.Y. Twentieth Century Fund 1964,
Buku Teks