Another clue perhaps. Look under Manufacturer:
http://www.deutsches-museum.de/en/fl...nes/horten-iv/
A note to Steve Coates:
I do not have this title but if you use the 'click to look inside' feature, it may contain the details you are looking for.
http://www.amazon.com/Aeronautical-R.../dp/354040645X
Regards,
Ed