Bartels, Robert
Richard D. Irwin, 1962
Buku Teks SO
Thomas, Susan J.
American Society for Training and Development Press, 2004
eBooks
United Nations Bureau of Social Affairs , 1955
Buku Teks SO
Raine, Kathleen, 1908-2003
British Council by Longmans, Green, 1965
Buku Teks SO
Uqaili, Mohammad Aslam, editor
Springer, 2012
eBooks