A very interesting book is
Kabel und Leitungen - Aufbauelemente, Werkstoffe, Fertigungen
Translated in English: "Cables and conductors - Constructions, materials, manufacture"
It is written in German (from 1989) and it was printed in the German Democratic Republic (368 pages).
Probably it is a good idea to contact the company SKET Kabel- und Verseilmaschinenbau (
www.sketvmb.de )
and ask them if they have a version in English.
Probably it is also a good idea to contact the following organization and ask for information written in English.
Fachverband Kabel und isolierte Drähte
Minoritenstraße 9-11
50667 Köln
Germany
Tel. +49221 96228 0
Fax +49221 96228 15
info@kabelverband.org
Best regards
Juan Carlos González Villar
www.kabelconsulting.de