http://netbsd.i2p/releases/formal-5/NetBSD-5.1.html
It represents a selected subset of
fixes deemed critical for security or stability reasons, as well as new
features and enhancements. Please note that all fixes in security/critical updates (i.e., NetBSD 5.0.1,
5.0.2, etc.) are cumulative, so the latest update contains all such fixes
since the corresponding minor release.