According to my copy to ANSI standard Z39.9-1979, "An ISSN is composed of seven
decimal digits plus an eighth check digit. The check digit is calculated as
outlined in Appendix A."

Revisions to this standard were recently balloted and approved. I trust that
these revisions do not affect the basic structure of the code.

Hunter Kevil
Product Specialist, Acquisitions and Serials
Data Research Associates