While his sons overcame pockets of resistance on the mainland, on 5 November 1139 Roger returned to Palermo to plan a great act of legislation: the Assizes of Ariano, an attempt to establish his dominions in southern Italy as a coherent state. He returned to check on his sons' progress in 1140 and then went to Ariano, a town central to the peninsular possessions (and a centre of rebellion under his predecessors). There he promulgated the great law regulating all Sicilian affairs. It invested the king and his bureaucracy with absolute powers and reduced the authority of the often rebellious vassals. While there, centralising his kingdom, Roger declared a new standard coinage, named after the duchy of Apulia: the "ducat."