\item \helpref{wxHtmlHelpController}{wxhtmlhelpcontroller}, a sophisticated help controller using \helpref{wxHTML}{wxhtml}, in
a similar style to the Microsoft HTML Help viewer and using some of the same files.
Although it has an API compatible with other help controllers, it has more advanced features, so it is
-recommended that you use the specific API for this class instead. Note that you
+recommended that you use the specific API for this class instead. Note that if you
+use .zip or .htb formats for your books, you
must add this line to your application initialization: \verb$wxFileSystem::AddHandler(new wxZipFSHandler);$
or nothing will be shown in your help window.
\end{itemize}