García Durán, Laura. “The Intervention of Innocent III in the Matrimonial Politics of Philip Augustus of France and of Alfonso IX of León”. Revista De Investigación De La Cátedra Internacional Conjunta Inocencio III, vol. 1, no. 3, Oct. 2016, pp. 221-45, https://vergentis.ucam.edu/index.php/vergentis/article/view/34.