Stilwell, Alexander, author
Chancellor Press, 2000
Buku Referensi
Adler, John H., author
Stanford University Press , 1951
Buku Teks
Schlesinger, Yames R.
Frederick A. Praeger, 1960
Buku Teks
Speas, R. Dixon
MGraw-Hill , 1955
Buku Teks
Deasy, George F.
New York,N.Y. J.B. Lippincott Co. 1958,
Buku Teks