Boyd, Harper W., Jr., author
Richard D. Irwin, 1956
Buku Teks
Kress, George
Prentice-Hall, 1988
Buku Teks
Parasuraman, A., author
Addison-Wesley , 1991
Buku Teks
Breen, George Edward, 1911-, author
McGraw-Hill , 1982
Buku Teks
Crimp, Margaret, author
Prentice-Hall, 1995
Buku Teks