United States. Department of Labor
Illinois : The United States Departemen of Labor, 1994, 1995
Buku Referensi
Turner, Paul, author
Macmillan, 1994
Buku Referensi
edited by Robert J. Gatchel, Izabela Z. Schultz
Springer, 2012
eBooks
edited by Julia Smedley, Finlay Dick and Steven Sadhra
Oxford University Press, 2013
Buku Teks
Europa Publication Limited, 1994
Buku Referensi