Start with some general search terms like:
Koran
Islam
Crusades
Use the boxes on the left side of the screen to check out Subjects which might help narrow down your search. Here are some sample subjects if you do a search for Koran.
Arab Historians of the Crusades by 
An Arab-Syrian Gentleman and Warrior in the Period of the Crusades by 
The Book of Contemplation by 
Crusaders and Muslims in Twelfth-Century Syria by 
The Crusades by The Crusades by The Damascus Chronicle of the Crusades by 
Defenders of the Holy Land by 
The Experience of Crusading by European Jewry and the First Crusade by History of the Expedition to Jerusalem, 1095-1127 by 
The Holy War Idea in Western and Islamic Traditions by The Knights of St. John in Jerusalem and Cyprus, c. 1050-1310 by 
The New Oxford Annotated Bible with the Apocrypha by De profectione Ludovici VII in orientem. The journey of Louis VII to the East by 
Ch 3: Quantum praedecessores: The Crusade Appeal of Pope Eugenius III in The Second Crusade by 
Robert the Monk's History of the First Crusade by 
The Second Crusade and the Cistercians by 
The Second Crusade by The World of the Crusaders by 
