Rowland, Diane
Cavendish Publishing Limited, 2000
Buku Teks
Houndmills Macmillan 1990,
Buku Teks
Harrington, Jon
Prentice-Hall, 1991
Buku Teks
Attwood, Gaynor
McGraw-Hill, 1989
Buku Referensi
Reynolds, George Walter, 1944-
Cengage Learning, 2019
Buku Teks