Powell, J. M. (2014). The Papacy, Frederick II and communal devotion in medieval Italy. Variorum collected studies series.
芝加哥风格引文Powell, James M. "The Papacy, Frederick II and Communal Devotion in Medieval Italy." Variorum Collected Studies Series 2014.
MLA引文Powell, James M. "The Papacy, Frederick II and Communal Devotion in Medieval Italy." Variorum Collected Studies Series, 2014.
警告：这些引文格式不一定是100％准确.