On 8/5/14, 3:13 AM, Juha Hakala wrote:
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Sadly especially libraries took their part in blurring that semantics,
but that is a different story.

Can you elaborate a bit what you mean by this?

Thomas may be referring to the usage in the MARC format:

$a - International Standard Book Number

Valid ISBN. ISBN and the embedded hyphens may be generated for display.

020 ##$a0491001304

As you can see, the hyphens are removed, and the ISBN is a single string of 0-9,X. "Valid ISBN" there does not refer to the form (e.g. removed hyphens) but to the fact that there is another subfield for ISBNs that have either been assigned to the MARC or that appear on the actual book that have later turned out to be invalid in some way (re-used, typo'd, etc.)

Karen Coyle
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