Smith, Brenda D., author
Longman, 2000
Buku Teks
Youth Coordination Centre International, 2003
Buku Teks
Wallace, Catherine, author
1992
Buku Teks
Wallace, Catherine, author
Oxford University Press, 1993
Buku Teks
Lean Mei Li, Mya Khemlani David, Ngew Yeok Meng, editor
University of Malaya, 2011
Buku Teks