That's a cool article on Baran, it looks like he predicted Amazon in 1968, and they were experimenting with early email type systems in that time, too. I'm sure the bulletin board followed shortly after.
Baran's full set of monographs written for RAND are now freely available online. I'd asked a couple of years ago if they might include one specifically, and they published the whole lot. Asking nicely works, sometimes.
Brotherton wrote a book on Masers and Lasers in 1964, you might find more info in that: https://www.amazon.com/Masers-Lasers-They-Work-What/dp/B0000...
is that the one you mean?