there are two of them. The PAGE\_CHANGING event is sent before the current
page is changed. It allows to the program to examine the current page (which
can be retrieved with
-\helpref{GetOldSelection()}wxnotebookeventgetoldselection}) and to veto the page
+\helpref{GetOldSelection()}{wxnotebookeventgetoldselection}) and to veto the page
change by calling \helpref{Veto()}{wxnotifyeventveto} if, for example, the
current values in the controls of the old page are invalid.