1. A. Becker, Papst Urban H (1988-1099), 2 vols (Stuttgart, 1964), vol. 1, pp. 24-78
2. J. Riley-Smith, The First Crusade and the Idea of Crusading (London, 1993), p. 12.
3. J. Flori, 'L'Eglise et la guerre sainte: de la paix de Dieu a la croisade', Annales: Economies, SociEtés, Civilisations, 47 (1992), 88-99
4. H. E. J. Cowdrey, 'From the Peace of God to the First Crusade', in La primera cruzada novecientos arios después: el concilio de Clermont y los origenes del movimiento cruzado, ed. L. Garcia-Guijarro Ramos (Castello d'Impressio, 1997), pp. 51-61
5. J. Flori, 'De la paix de Dieu a la croisade? Un réexamen', Crusades, 2 (2003), 1-23. The most famous statement of the case is by C. Erdmann, Die Entstehung des Kreuzzugsgedankens (Stuttgart, 1935), translated by M. W. Baldwin and W. Goffart as The Origin of the Idea of Crusade (Princeton, 1977), pp. 59-67, 75-7. For a contrary view, see M. Bull, Knightly Piety and the Lay Response to the First Crusades: The Limousin and Gascony, c. 970-c. 1130 (Oxford, 1993), pp. 20-69.