Machin, Linda
Longman Information and Reference, 1993
Buku Teks
Rutter, Michael, author
Cambridge University Press, 1998
Buku Teks
Maggie Robson; Sue Pattison, editor
Sage, 2018
Buku Teks
HMSO , 1995
Buku Teks
Jossey - Bass Publishers, 1995
Buku Teks