Revised definition for ISBN:
"A unique standard identifier (ISO 2108) used to identify monographic publications (books). ISBN-13 is required. E-ISBN is the expected value, with print ISBNs provided only where E-ISBN is not available. ISBN-13 MUST be formatted as follows: the string MUST include four hyphens, the first of which appears after the first three digits and the last of which appears before the last digit. There must be at least one digit between each of the four hyphens in the ISBN-13. ISBN-10 MUST NOT be used."
Add definitions from COUNTER best practices, excluding AI which has been postponed to R5.1.2 (#359).
Revised definition for ISBN:
"A unique standard identifier (ISO 2108) used to identify monographic publications (books). ISBN-13 is required. E-ISBN is the expected value, with print ISBNs provided only where E-ISBN is not available. ISBN-13 MUST be formatted as follows: the string MUST include four hyphens, the first of which appears after the first three digits and the last of which appears before the last digit. There must be at least one digit between each of the four hyphens in the ISBN-13. ISBN-10 MUST NOT be used."
Add definitions from COUNTER best practices, excluding AI which has been postponed to R5.1.2 (#359).