<para>Note that the files in the <filename>/etc/apt/preferences.d</filename>
directory are parsed in alphanumeric ascending order and need to obey the
-following naming convention: The files have no or "<literal>pref</literal>"
-as filename extension and which only contain alphanumeric, hyphen (-),
+following naming convention: The files have either no or "<literal>pref</literal>"
+as filename extension and only contain alphanumeric, hyphen (-),
underscore (_) and period (.) characters.
Otherwise APT will print a notice that it has ignored a file if the file
doesn't match a pattern in the <literal>Dir::Ignore-Files-Silently</literal>
expressions surrounded by /. For example, the following
example assigns the priority 500 to all packages from
experimental where the name starts with gnome (as a glob()-like
-expression or contains the word kde (as a POSIX extended regular
+expression) or contains the word kde (as a POSIX extended regular
expression surrounded by slashes).
</para>
<para>
The rule for those expressions is that they can occur anywhere
-where a string can occur. Those, the following pin assigns the
+where a string can occur. Thus, the following pin assigns the
priority 990 to all packages from a release starting with karmic.
</para>