Cat Russo, editor
American Society for Training & Development, 2011
eBooks
Glaspell, S., author
Frederick A Stokes Company, 1931
Buku Teks
No, Yang-gyun, author
Han'guk Munhwasa, 2002
Buku Referensi
Holt, Edwin B. (Edwin Bissell), 1873-1946
Macmillan, 1974
Buku Teks
London: Tiger Books International, 1994,
Buku Referensi