That ain't the mind-boggling article, you can find *that* here: [cs.cornell.edu...]
The link above gives you some idea of Kleinberg proposes to determine computationally what's an authority site. It's actually pretty readable, and since I'm sure it's not going to get widely read, I'll boil down the answer to the OP's questions here:
What in your opinion makes an authority site?
In Kleinberg's opinion, it's inbound link structure.