Freedman, Alan
Amacom, 1995
Buku Referensi
Greenfield, Jane
Oak Knoll Press, 1998
Buku Teks
Andersen, Dines
Copenhagen: Gyldendalske Boghandel, 1907
Buku Teks
American Psychiatric Press, 1984
Buku Referensi
New York Institute of Finance, 1988
Buku Teks