| http://www.w3.org/ns/prov#value | - The cover layer(s) may include any materials known to those of ordinary skill in the art, including thermoplastic and thermosetting materials, but preferably include ionic copolymers of ethylene and an unsaturated monocarboxylic acid, such as SURLYN???, commercially available from E. I. DuPont de Nemours & Co., of Wilmington, Del., and IOTEK??? or ESCOR???, commercially available from Exxon.
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