How to find and/or REINDEX only GiST indexes in the database?

Hi,

We're planning to upgrade our Production server from PostgreSQL v8.2.3 to
the latest version in 8.2 series, that is v8.2.22.

In 8.2.11 Release Notes here
http://www.postgresql.org/docs/current/interactive/release-8-2-11.html, it's
been mentioned that:
"Also, if you were running a previous 8.2.X release, it is recommended to
REINDEX all GiST indexes after the upgrade."

My question is, how do I find out or REINDEX *only* GiST indexes in the
database?  Is there a single syntax/command that does this?

Regards,
Gnanam