Gunter,
Keep in mind that the document Ivan kindly proposed is still work in process... and that the last has not been mentioned about it.
It is a good initial reference for this point in time, but to 'formaly' reference to it would result in a moving target I fear.
let me correct that. the document is done. and will be published as an RFC shortly. to provide the background. -07 was sitting in the RFC editor queue awaiting normative referenced documents to progress. because of some issues with broken host implementations and multiple prefixes, we chose to reiterate the document one more time, to lessen the change of dual stack breakage. -09 is now making its way back onto the queue. (since the referenced documents are still to be published this did not in any way delay the CPE router draft). cheers, Ole