| Subject: | ean_to_isbn should not support converting 979 EANs |
The 979 EANs can never be successfully converted to an ISBN number because there is no valid mapping (see explanation below). Only 978 should be supported.
http://www.bookweb.org/education/6865.html
"13-digit ISBN: The current 10-digit ISBN will be restated as a 13-digit EAN by dropping the final check digit, adding a leading "978" to the remaining 9-digit "core" and calculating a new, modulus-10 check digit."
"However, when all numbers in a given "978" block have been assigned, national ISBN agencies will begin assigning 13-digit ISBNs with a "979" prefix to subsequent requests. This can result in two entirely different books having the same nine-digit "core" of the ISBN, one with a "978" prefix and the other with a "979", and with different check digits. At that point, the current practice of scanning the Bookland EAN, stripping off the 978, recalculating the check digit and storing the resulting 10-digit ISBN in a database will produce the same ten-digit ISBN for both books sharing the same nine-digit core. This practice will at that point cease to be a viable solution."