Book with multiple authors

iTunes/iBooks won't display multiple authors entered separately in the EPUB opf file.

The books that display multiple authors in my library are the ones purchased on the iBookstore, and this data seems to be taken from the iTunesMetadata plist.

Would it make sense to generate a metadata plist for books not released on iBookstore? Or is this only done when submititng through iTunes Producer?

Is there another way to display multiple authors (two) in iTunes or iBooks library?

Thanks!

Jean-Michel