Author,Title,Edition,Publisher,Year,Series,Number,ISBN,ISSN,URL
"Williams, William Klapp",The communes of Lombardy from the VI. to the X. century : an investigation of the causes which led to the development of municipal unity among the Lombard communes,,Johns Hopkins Press,1891,The Johns Hopkins University studies in historical and political science,,,,https://cir.nii.ac.jp/crid/1130000794866400512