REVIEWSThe author interprets these artistic expressions of the quadripartite and rotational nature of the Chacs (good times follow bad times) as a symbolic model of the political system that limited rulers' tenure to twenty-year terms. Masterkey Rosemary Sharp analyzes the T, step-fret, and composite mask motifs of the Epiclassic period, and also relates these architectural motifs to the ideological and political systems.