Choisgallery
Choi's Gallery , 2009
Buku Referensi
Overton, Grant
Funk & Wagnalls Company, 1927
Buku Teks
Trifoni, Jasmina
White Star Publishers, 2013
Buku Referensi
Macmillan, 1996
Buku Referensi
Phillips, Jack J.
American Society for Training and Development Press;, 2005
eBooks