Liddell, Ken
Western Producer Prairie Books, 1977
Buku Teks
Hart, B.H. Liddell
Frederick A. Praeger, 1961-1965
Buku Teks
Liddell, Alix
Frederick Muller, 1970
Buku Teks
Reich, Robert B.
Boston, 2002
Buku Teks
Meyer, Kathy, author
[American Society for Training & Development;, ], 1997
eBooks