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  https://dataswamp.org/~incal/books/isbn.txt             incal@dataswamp.org
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                             the ISBN & ISSN file
                            by Emanuel Berg (incal)
                              updated 2024-05-22


ISBN = International Standard Book Number

ISBNs are purchased from the International ISBN Agency.                     [1]

ISBN-10 and ISBN-13 have this structure:

  -----------------
  0    1    2   3 4  <- field
  -----------------
      81-7525-766-0  <- ISBN-10 (1970-2007)
  978-81-7525-766-5  <- ISBN-13 (2007-)

Field overview:

  0  GS1 prefix          978 (or 979), ISBN-13 only                         [2]
  1  registration group  the country                                        [3]
  2  registrant          the publisher
  3  publication         the book
  4  check digit         computed from previous digits

Field 1 - the registration group:

  0 or 1   English speaking country
       2   French ditto
       3   German ditto
       4   Japan
       5   Russia
     ...   ...
       7   China
      84   Spain (Spain and only Spain; compare the top 1-3!)
      91   Sweden
     988   Hong Kong
   99936   Bhutan

Field 2 - the registrant:

  Assigned to the publisher by the national ISBN agency.

Field 3 - the publication:

  Assigned by the publisher, within a range.

Field 4 - the check digit:

  ISBN-10: A single digit, 0-9, or the letter X, to denote 10
  ISBN-13: A single digit, 0-9

The ISBN-10 check digit:

  If

    d_1  d_2  d_3  d_4  d_5  d_6  d_7  d_8  d_9

  are the first 9 digits of an ISBN-10 from left to right,
  then the 10th digit, the check digit, is equal to

    (11 - (10 * d_1 +
            9 * d_2 +
            8 * d_3 +
            7 * d_4 +
            6 * d_5 +
            5 * d_6 +
            4 * d_7 +
            3 * d_8 +
            2 * d_9) % 11) % 11

  If the check digit is 10 it is denoted X. This is so that
  all ISBN-10 will be of the same length despite the presence
  of the two-digit 10 data item.

The ISBN-13 check digit:

  If d_1 up and until d_12 are the first 12 digits of an
  ISBN-13, then the 13th, check digit is equal to

    10 - ((1 *  d_1 +
           3 *  d_2 +
           1 *  d_3 +
           3 *  d_4 +
           1 *  d_5 +
           3 *  d_6 +
           1 *  d_7 +
           3 *  d_8 +
           1 *  d_9 +
           3 * d_10 +
           1 * d_11 +
           3 * d_12) % 10)

ISSN:

  ISSN = International Standard Serial Number (ISO 3297, 1975)

  For example, The Ring Magazine has ISSN 0035-5410.

The ISSN format:

  d_1  d_2  d_3  d_4  -  d_5  d_6  d_7  c

  d_i (for i in 1-7) is a single integer.

  c, the check digit, is 0-9 or X, to denote 10.

The algorithm to compute the check digit c:

  c' = (8 * d_1 *
        7 * d_2 *
        6 * d_3 *
        5 * d_4 *
        4 * d_5 *
        3 * d_6 *
        2 * d_7) % 11

      { 0        (c' = 0)
  c = {
      { 11 - c'  (c' ≠ 0)

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[1] https://en.wikipedia.org/wiki/International_Standard_Book_Number
[2] https://en.wikipedia.org/wiki/GS1
[3] https://en.wikipedia.org/wiki/List_of_ISBN_identifier_groups

test data: https://dataswamp.org/~incal/books/books.bib

   verify: https://dataswamp.org/~incal/emacs-init/isbn-verify.el
           https://dataswamp.org/~incal/emacs-init/issn-verify.el
           https://dataswamp.org/~incal/emacs-init/bibtex/bibtex-incal.el
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