Beer, Stafford
John Wiley & Sons, 1981
Buku Teks
Rugman, Alan M.
McGraw-Hill , 1985
Buku Teks
Thompson, Arthur A., 1940-
Prentice-Hall, 1989
Buku Teks
edited by G.C. Archibald
Penguin Education, 1971
Buku Teks
Rugman, Alan M.
McGraw-Hill, 1985
Buku Teks