Vernon, Raymond, author
Free Press, 1989
Buku Teks
Thorp, Willard L., author
John Hopkins Press, 1954
Buku Teks
Stanley, Timothy W., author
Westview Press, 1982
Buku Teks
Government Printing , 1977
Buku Teks
Hailstones, Thomas J., author
South-Western Publishing, 1985
Buku Teks