Carter, Linda, author
West, A Thomson Reuters Business, 2011
Buku Teks
Stephan, Frederick F.
Chapman & Hall , 1958
Buku Teks
Wenger, Leopold, author
Veritas press, 1940
Buku Teks
Karlen, Delmar
West, 1972
Buku Teks
Blume, William Wirt
Prentice-Hall, 1955
Buku Teks