A numeric type of identifier for books. It consists of a 13- or 10-digit code. Usually (but never always), it starts with "978", is separated by hyphens (e.g., 978-4-06-178955-5, 978-4-8402-2466-6, 978-1-63442-060-0, 4-09-137351-8) and displayed with a barcode.
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