ISSN ASSIGNMENT

ISSN assigned to print publications
ISSN assigned to non-print publications
Is the same ISSN really always assigned to the issues of a journal, series, etc.?
Why have an ISSN at all when an ISBN is available?

ISSN assigned to print publications 

• Journals
  Please imprint the ISSN in the same and very visible place (as well as, if possible, on the imprint page) on the outside cover of each issue, volume, year, etc., preceded by the letters "ISSN" in accordance with the following example: ISSN 1234-5678.
  Please note: The last digit is a check digit; it is represented as an "X" if it has the numerical value of 10.
  The typography is largely left up to you. The ISSN should be imprinted in such a way, however, that one can still read it from a greater distance.  Accordingly, in addition to the ISSN, it is also advisable to specify the volume (or, alternately, the year) number, date of publication and issue number of each issue. 
• Sets of writings (book series), supplement series, journal-like series (annuals), annual reports, etc.
  For these publications, the ISSN appears either alone, partly in combination with an ISBN and/or with an additional ISSN, as follows:
  ISSN alone
  In this case, imprint the ISSN on the outer cover (not on the dust jacket, however) and/or on the imprint page.
  ISSN and ISBN
  In this case, imprint the ISSN (for the series) combined with, i.e. in close proximity to, the ISBN (of the respective volume) according to the following example:
  ISSN 1234-5678
  ISBN 3-494-00373-4
  ISSN and ISSN
  If two ISSNs are to be assigned to an issue, volume or year, please imprint both numbers on the outer cover (not on the dust jacket, however) and/or on the imprint page in close proximity to each other; in doing so, indicate after each number the title of the respective series in parenthesis according to the following example:
  ISSN 0341-0943 (Jahrbuch für kritische Medizin)
  ISSN 0341-3039 (Argument-Sonderbände)
  ISSN, ISSN and ISBN
  If two ISSNs as well an ISBN are to be indicated for an issue, volume or year, please imprint both ISSNs (for the series) together with, i.e. in close proximity to, the ISBN (of each particular volume); in doing so, please indicate after each ISSN the title of the respective series in parenthesis according to the following example:
  ISSN 0341-0943 (Jahrbuch für kritische Medizin)
  ISSN 0341-3039 (Argument-Sonderbände)
  ISBN 3-920037-40-5

ISSN assigned to non-print publications

For non-print publications, please display the ISSN on an internal source, e. g. on the title page or imprint page. Other possible locations on non-print publications are on external sources, e. g.  CD-ROMs, DVDs, cassettes, disc labels or containers. As explained above regarding print publications, as a rule the numbers should appear in the same, readily visible place for each issue, volume, year, etc.

Is the same ISSN really always assigned to the issues of a journal, series, etc.?

In contrast to ISBN, which changes from book to book, a new ISSN is only necessary if the title of a journal changes. That means that an ISSN remains actually unchanged in many cases, but this is not a hard-and-fast rule. Please inform us in a timely manner of any planned title change and assign the newly issued ISSN to the first edition under the new name.
A new ISSN, however, is not required due to changes of publisher, imprint or frequency of publication.

Why have an ISSN at all when an ISBN is available?

The purpose of the ISSN is to identify clearly serial publications such as journals or series as an overall whole; in contrast, the ISBN serves as an unmistakable designation of a single book. In the case of book series, supplement series, annuals, annual reports, etc., each individual volume can of course receive a unique ISBN insofar as it has the character of a monograph or is available individually. However, the entire series within which such volumes are published must get an ISSN. This is why publications frequently have an ISBN as well as an ISSN.