We would expect one ISSN because we assume the publications are identical.
In the world of serial multiple versions, the only place you find separate
ISSNs is where the new version is truly not the same thing as the
corresponding paper (or other original) title--to date particularly the
electronic journal, which ordinarily differs in coverage and other ways..
Even there the ISSN is the same if it remains a true reproduction (J-Stor
journals, which use bitmapped images of the original pages, have been
assigned the same ISSN as the print.)

Regards, Frieda
 ----------
Frieda Rosenberg
Serials Cataloging
Univ. of North Carolina at Chapel Hill
friedat@email.unc.edu

On Wed, 15 Oct 1997, Graham Barr wrote:

> Let's say that a periodical is published simultaneously in paper format
> and in microform.  Would this periodical have one ISSN or two different
> ISSN's (one for each format)?  I'm assuming it would have two
> bibliographic records (one for each format).
>
> Thank you.
>