Artikel Jurnal
Lientz, Bennet P.
Elsevier, 2004
Buku Teks SO
Basil Blackwell for the United Nations Industrial Development Organization, 1991
Buku Teks
editor, SPES
Gramedia Pustaka Utama V, 1994
Buku Teks
edited by Ivonne Audirac
John Wiley and Sons, 1997
Buku Teks SO