http://msen.com/~wei/JT-homepage.html http://spd.erim.org/jt_papers/ It now is available from John Trenkle's homepage., as papers/sdr94ps.gz.
I have applied the technique to implement a written language identification program. At the moment, the system knows about 69 natural languages (counting Esperanto as a natural language).
The textcat programme is not any langer actively maintained by me. However, the SpamAssassin spam filter programme includes a version of TextCat. They have been working on it some more, so perhaps you want to get their version from http://spamassassin.apache.org.