I was chewing on a problem with some tungsten cathodes in a pressure gauge. I knew that guys like Irving Langmuir had probably solved that problem a long time ago. After all, we have been putting incandescent tungsten in vacuum systems for more than a century. That started me on a search for old books.
My search took me to an unassuming, yet interesting place; www.tubebooks.org. This is a vast collection of out of print materials that have been scanned into PDF format. I did find some juicy books for vacuum tube technology and got some great insights into the problems of the day.
The site’s heading proclaims, “Herein you will find a collection of vintage engineering texts, vacuum tube datasheets, and other obsolete information, presented free of charge and without annoying advertisements.”