Sandys-Winsch, Godfrey, author
Shaw & Sons, 1993
Buku Teks
Daniels, Kathy, author
Chartered Institute of Personnel and Development, 2012
Buku Teks
Sweet and Maxwell, 1975
Buku Teks
Simpson, A.W.B., author
Clarendon Press, 1986
Buku Teks
Kingdom, Elizabeth F., author
Edinburgh University Press, 1991
Buku Teks