| 摘要 |
Jacket made up of a single sheet forming the cover, hinged down its middle width by virtue of a suitable perforation, reinforced by a flexible back, precoated with a coat of plastic resin, welded on the outside of the fold of the spine and coated along the inside middle crease with a heat-meltable plastic resin by which the leaves are bound in cooperation with a suitable heat apparatus. <IMAGE>
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