1. Hugh Kennedy, Crusader Castles (Cambridge, 1994), p. 98
2. Ronnie Ellenblum, Crusader Castles and Modern Histories (Cambridge, 2007), p. 189
3. Paul E. Chevedden, "Fortifications and the Development of Defensive Planning during the Crusader Period," in The Circle of War in the Middle Ages, ed. Donald J. Kagay and L. J. Andrew Villalon (Woodbridge, 1999), p. 34. The Hungarian scholar Erik Fugedi reached a very different conclusion while researching fortresses of the first half of the thirteenth century in Hungary. According to Fugedi, "Innovations in castle building during the thirteenth century were not triggered by advances in military technology, but rather by social development, enhanced by the Mongol invasion of Hungary in 1241." See Erik Fugedi, Castles and Society in Medieval Hungary (1000-1437) (Budapest, 1986), p. 42.
4. Christopher Marshall, Warfare in the Latin East, 1192–1291 (Cambridge, 1992), pp. 210–25. On Frankish siege warfare in the early decades of the crusader kingdom, see Joshua Prawer, The Latin Kingdom of Jerusalem: European Colonialism in the Middle Ages (London, 1972), pp. 344–451; Meron Benvenisti, The Crusaders in the Holy Land (Jerusalem, 1970), pp. 284–86; Ellenblum, Modern Histories, pp. 203–6.
5. Jonathan Riley-Smith, The Crusades: A Short History (London, 1990), p. 84