| http://www.w3.org/ns/prov#value | - A quantity of spherical balls I I, made of wood or preferably of a lightweight plastic such as polystyrene and colored in a variety of bright colors, used as counter pieces, are contained in a spherical enclosure I3, whose upper half 14 is a thin-walled transparent shell made of a high impact resistant plastic such as polypropylene modified polyvinyl chloride.
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