Angela Siegfried, editor
American Society for Training & Development, 2010
eBooks
Seidman, Dan
American Society for Training & Development, 2008
eBooks
Book House Training Centre/Unesco
Book House Training Centre, 1991
Buku Referensi
Sarah Nabilla Yasmin Riza
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2018
UI - Makalah dan Kertas Kerja
Carlaw, Peggy
McGraw-Hill, 1997
Buku Teks SO