=item C<create_version %attributes>
-Prerequisites: C<$self> must be a working copy (see L</working_copy>),
+Prerequisites: C<$self> must be a working copy (see the overview),
not a versioned copy.
This function creates a new version for C<$self>. This involves
=item C<invalidate_version>
-Prerequisites: C<$self> must be a working copy (see L</working_copy>),
+Prerequisites: C<$self> must be a working copy (see the overview),
not a versioned copy.
Sets the C<version_id> field to C<undef> and saves C<$self>.