+- Automake <http://www.gnu.org/software/automake/>
+- Autoconf <http://www.gnu.org/software/autoconf/>
+- Flex <http://www.gnu.org/software/flex/>
+- Gettext <http://www.gnu.org/software/gettext/>
+- Gzip <http://www.gnu.org/software/gzip/>
+- Tar <http://www.gnu.org/software/tar/>
+- Wget <http://www.gnu.org/software/wget/>
+
+As of this writing, the latest stable version of Gzip is 1.2.4 but we
+suggest using test version 1.3.5 (or later, if one becomes available).
+
+Valgrind <http://valgrind.org/> is also highly recommended, if
+Valgrind supports your architecture.
+
+Bison is written using Bison grammars, so there are bootstrapping
+issues. The bootstrap script attempts to discover when the C code
+generated from the grammars is out of date, and to bootstrap with an
+out-of-date version of the C code, but the process is not foolproof.
+Also, you may run into similar problems yourself if you modify Bison.