| http://www.w3.org/ns/prov#value | - a core including a center and at least one intermediate layer covering the center; and a polyurethane cover covering the core; wherein the polyurethane cover has a thickness of not more than 1 mm and is formed from a cured composition which contains an isocyanate group-terminated urethane prepolymer having an isocyanate component derived from at least one isocyanate compound selected from the grou
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