The ivreg2 routine of Baum, Schaffer and Stillman has been updated on
SSC to version 2.0.03. This routine, described in the authors' article
in Stata Journal 3:1, has been altered to handle an exactly-identified
difference-in-Sargan statistic ("C" statistic) properly, and to add the
score() option recently added to official ivreg. ivreg2 remains
avaiilable for version 7 or higher.