Anderson, Joyce I., author
American Management Association, 2007
eBooks
Skolnik, Lisa, author
Rockport Publisher, 2001
Buku Referensi
Nickell, Paulena
John Wiley & Sons, 1959
Buku Teks
Nickell, Paulena
Wiley Eastern, 1970
Buku Teks
Firth, Rosemary, author
Humanities Press, 1966
Buku Teks