Hello,
Here I have found a site with over a hundred old books in PDF:
https://web.archive.org/web/20131210025900/http://www.vintageradio.com/index.php?a=28&b=153
Bertus
Here I have found a site with over a hundred old books in PDF:
https://web.archive.org/web/20131210025900/http://www.vintageradio.com/index.php?a=28&b=153
Bertus