[Pharo-users] Voyage: how to delete references to objects.

Hi, I'm using Voyage in a Pharo application. I have two MongoDB collections which are ComicsCollection and ComicsBook. Each book is attached to a instance of ComicsCollection. The reference of each book is stored in an ordered collection (in the instance of ComicsCollection). The problem is that if I remove a book, the reference to the book is not deleted from ComicsCollection. How can I remove properly a book and the reference to the book ? Best regards Olivier ;-)