edited by Joseph Seibert & Gorden [i.e. Gordon] Wills
Penguin Books, 1970
Buku Referensi
edited by Keith K. Cox
Appleton-Century-Crofts, 1967
Buku Teks
Baker, Michael J.
Macmillan, 1991
Buku Teks
Kress, George
Prentice-Hall, 1988
Buku Teks
Parasuraman, A.
Addison-Wesley, 1991
Buku Teks