The second part to his book 'Sufism' http://www.fethullahgulen.org/content/category/14/281/51/ He talks about Ma'rifa Hikma Wilaya Riyada Hurriya ightirab istighraq ghayba tajrid baqa' bilAllah Wujud Suroor Muhasaba talbis Chila Dervish Mujahada tafrid farq ..and many others In the origin of sufism, he mentions Al-Wasaya wa al-Ri'aya (The Advices and Observation of Rules) by Sayyiduna Harith al-Muhasibi radyAllahu anhu, Al-Risala al-Qushayri of Sayyiduna Imam al-Qushayri radyAllahu anhu, Ihya 'uloom al-Din the majestic of Hujjatul Islam Sayyiduna Imam al-Ghazali radyAllahu anhu
http://www.fethullahgulen.org/content/category/5/156/50/ Please read Futuwwa (Youth and Chivalry) The complete list of pages in the booklet is big. Some of the subjects he talks about the origin of sufism Qalb Qurb Raja' irada murid muraad Faqr Ghina Hal Maqam Haya Huzn istiqama khauf khashya ihsan ikhlas inbisat
