The book "Communities of Lombardy from the 6th to the 10th centuries. A study of the reasons that led to the development of municipal unity among the Lombard communities" is written by the author William Klapp Williams. This work examines in detail the history of the communities of Lombardy, starting from the 6th century and ending with the 10th century. The author examines the reasons that contributed to the formation of municipal unity and interaction among local communities in this region. Through a close study of documents and sources of the time, Williams reveals important aspects of the social, economic and political development of the communities of Lombardy, making a significant contribution to the study of the history of the region and the understanding of the formation of municipal structures in Western Europe.