Here's a technical whitepaper written by Craig Calfee back in 1994. There is also an updated version of the document. In the original, note that he describes different joining methods. He also provides examples of Trek that used carbon tubes joined to bladder-molded carbon lugs. He also points out to another example of CF tubes bonded to CF lugs with the Peugeot Carbon Pro. Admittedly, he does not describe his joining method for the Carbonframe bikes he was producing at the time as using carbon lugs. Actually he calls the process lugless. However, if you read carefully, you will notice that what he's in fact doing is creating the lug at the time of joining the tubes by molding them [lugs] into place during the joining process. The result is technically a lugged construction without the traditional post-process joining using adhesives or similar bonding methods.