Feild, R. (2002). The last barrier: A journey into the essence of Sufi teachings (25th anniversary edition.). Lindisfarne Books.
Chicago-referens (17:e uppl.)Feild, Reshad. The Last Barrier: A Journey into the Essence of Sufi Teachings. 25th anniversary edition. Great Barrington, MA: Lindisfarne Books, 2002.
MLA-referens (9:e uppl.)Feild, Reshad. The Last Barrier: A Journey into the Essence of Sufi Teachings. 25th anniversary edition. Lindisfarne Books, 2002.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.