Khan, Hazrat Inayat
The Sufi International Headquarter's, 1956
Buku Teks
Copenhagen : C.W.K. Gleeup Lund
Majalah, Jurnal, Buletin
editor, Cynthia Macdonald and Garaham Macdonald
Blackwell Publishers, Ltd., 1995
Buku Teks
edited by Robert J. Sternberg
American Psychological Association, 2005
Buku Teks
Royce, James E.
McGraw-Hill, 1961
Buku Teks