How to UN-merge books

[Linguana]

Hello there.

I was going through my "duplicates" and "The Last Unicorn" (in English) showed up with "Die Sonate des Einhorns" (German). However, this is not the same book. It is listed as two editions of one book, but the German one is "The Unicorn Sonata" by Peter S. Beagle.

Now I've been browsing the librarian-forum but I couldn't find how to un-merge this editions and add the German version to the proper English book (Unicorn Sonata, that is). I don't dare simply merging them, for fear that the two books will be completely merged (showing up as one and the same, even in English).

Help?

[Linguana]

Already fount out how it works and fixed it. Thanks. :)