I went back to the start of the thread to capture local copies of the various cited references. Most of the links are dead, however, internet archive wayback machine got me to almost all of them, so I have the files cached here now (mostly commercial reference material from HP and Boonton, along with Tobias' hand drawn schematics (I don't believe Tobias published schematics after his first few drafts, and don't know if he maintains a repository anywhere.)