There are tons of media articles, conferences, books, and other mentions of MUD1 and Bartle, including prominent newspapers, magazines, etc. The MUD1 story is all over the place.

As for your comment "not any Stanford affiliated source" -- if you read the Gamasutra story carefully it has a prominent link to a Standford website page (on game history!) talking about, in its first sentence even,"the first online virtual world, MUD1."