# ISBN

Internation Standard Book Number: A 9 digit number, divided with hyphen with a control digit, which can be 0...9 or X.

Value type of the APE key ISBN.

Check of correctness:

N1 N2 N3 N4 N5 N6 N7 N8 N9 - Nchk

The following equation must be fullfilled:

(2 N1 + 3 N2 + 4 N3 + 5 N4 + 6 N5 + 7 N6 + 8 N7 + 9 N8 + 10 N9) MOD 11 = Nchk A value of 10 for Nchk is encoded as a X.

Examples:

- 3-89319-434-7
- 3-05-500074-9
- 0-201-54199-8
- 3-341-00480-7
- 3-341-00488-X