Bottherill, George
Cambridge University Press, 1999
Buku Teks
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
Malik B. Badri
Pustaka Firdaus, 1989
Buku Teks