There may be multiple MDI parent frames in a single application, but this probably only makes sense
within programming development environments.
-Child frames may be either \helpref{wxMDIChildFrame}{wxmdichildframe}, or \helpref{wxFrame}{wxframe}.
+Child frames may be of class \helpref{wxMDIChildFrame}{wxmdichildframe} (contained
+within the parent frame) or \helpref{wxFrame}{wxframe} (shown as a top-level frame).
An MDI parent frame always has a \helpref{wxMDIClientWindow}{wxmdiclientwindow} associated with it, which
is the parent for MDI client frames.