The variety of styles that arose in the sixteenth century all but defies classification. Goldthwaite notes that Paride Berardi's morphology of Pesaro maioliche comprises four styles in 20 sub-groups; Tiziano Mannoni categorized Ligurian wares in four types, eight sub-categories and 36 further divisions; Galeazzo Cora's morphology of Montelupo's production is in 19 groups and 51 categories. The diversity of styles can best be seen in a comparative study of apothecary jars produced between the 15th and 18th centuries. Italian cities encouraged the pottery industry by offering tax relief, citizenship, monopoly rights and protection from outside imports.