REMARK: Variations 001ng and 002ng may produce error 60523 depending on implementation.

REMARK: Although these variations each show only one error code, depending on a vendors' implementation, validation errors may occur prior to the error listed, or other errors may cascade after Footnote-Substitution-Group. In particular, the schema fales of the ng variations should throw error 6.7.27 because they use a substitutionGroup disallowed by that rule; the point being that 6.7.27 would not apply to a standard taxonomy but 6.5.27 would still be an error. As long as all variations marked NOGOOD are rejected because of the disallowed substitutionGroup, a validator may be considered as legitimately passing this testcase.