prov:value
| - The walls of the confined zone may be conventional substantially gas-impermeable packaging materials like glass, methylmethacrylate, polystyrene and polyethylene, as in bottles, jars, flasks and tubes; sheets, especially thermoplastic, heat-scalable films like polyvinylidene chloride, polyethylene terephthalate, copolymers of vinylidene chloride and vinyl chloride, polyethylene, cellophane, plasti
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