Our grandfathers knew. Another brilliant paper on electron tube noise.

Limits to Amplification - J. B. Johnson and F. B. Llewellyn

https://ia601902.us.archive.org/12/items/bstj14-1-85/bstj14-1-85.pdf

Also this:
http://www.keith-snook.info/Stuff-you-should-read/Frederick%20Britton%20Llewellyn%20-%20Noise%20in%20Vacuum%20Tubes%20and%20Attached%20Circuits.pdf


And this:
https://ia800308.us.archive.org/21/items/bstj13-4-634/bstj13-4-634.pdf