Delete purchased books from Reader PC app

How do I delete purchased books from the Sony PC Reader app? I "purchased" a children's Christmas book and a recipe book for $0 each. I do not need them, but cannot delete them. The help file says they cannot be deleted from the app - surely they can be deleted from the Sony Store.

Many thanks for any help,

Richard.

UPDATE: Okay I got the answer - cannot be done. I will try Sony to see if they can help. Maybe they can do it manually. Not overly impressed with their software - but need it to sync highlights on nonDRM sideloaded books.