McGowan, Maryrose
John Wiley & Sons, [Date of publication not identified]
Buku Teks SO
Delmon, Jeffrey
Sweet & Maxwell, 2000
Buku Teks
edited by A.D. Austen, R.H. Neale
International Labour Office, 1995
Buku Referensi
Piotrowski, Christine M.
Wiley, 1999
Buku Teks
Foster, Kari
John Wiley & Sons, 2007
Buku Teks