% epubcheck mercredifiction.epub
Validating against EPUB version 3.0 - custom validation
Validating using EPUB version 3.0 rules.
WARNING(OPF-007): mercredifiction.epub/EPUB/content.opf(2,142): Re-declaration of reserved prefix
'rendition'.
ERROR(RSC-005): mercredifiction.epub/EPUB/content.opf(7,30): Error while parsing file 'assertion f
ailed: Duplicate ID 'creator''.
...