[ColinWright]

In case the author is following this:

Typo:

It’s worth noticing that this definition is not in general transitive: we may well have three documents A,B,C such that S(A,B)≥S_{crit} and S(B,C)≥S_{crit} but S(A,B)<S _{crit}

That last S(A,B) should be S(A,C).

(Unless I'm very much mistaken ... and I could be)