Youth Coordination Centre International, 2003
Buku Teks
Suzuki, Kazuhito, author
Springer Nature, 2019
eBooks
Smith, Brenda D., author
Longman, 2000
Buku Teks
Jones-Brown, Delores D., author
Pearson/Prentice Hall, 2004
Buku Teks
Lean Mei Li, Mya Khemlani David, Ngew Yeok Meng, editor
University of Malaya, 2011
Buku Teks