Andrain, Charles F., author
Macmillan, 1995
Buku Teks
edited by George Dalton
New York, 1971
Buku Teks
Smith, Anthony D., author
Longman, 1976
Buku Teks
Smith, Anthony D., author
Longman, 1976
Buku Teks
Crompton, Roseemary
Unwin Hyman, 1990
Buku Teks