I don't think you're going to find that in BOL, Chris; unless I am mistaken LEAD and LAG are not supported by SQL Server. Oracle uses them to access values in a previous or next row - see this article. Let's hope Microsoft adds them to a future version of SQL Server.

Kevin, I too am curious about the performance of your method on large data sets. Doing a self-join with a WHERE a < b condition generally leads to very slow queries as the table gets large - a triangular join has Order N² performance. But using a partition ought to be much more efficient.