Burckhardt, Titus. An introduction to Sufi doctrine (Lahore, Sh. M. Ashraf [1959]). Thomas Merton's Marginalia Collection.

For references to this book in Merton's journals and published correspondence, see also: http://www.merton.org/research/Quotations/results-b.asp?phrase=Burckhardt.

See accompanying link to Bellarmine University library catalog for the publisher and other bibliographic information.