If two or more inventions are claimed in a single application, and are
regarded by the Office to be of such a nature that a single patent
should not be issued for both of them, the applicant will be required to
limit the application to one of the inventions. The other invention may
be made the subject of a separate application which, if filed while the
first application is still pending, will be entitled to the benefit of
the filing date of the first application. A requirement to restrict the
application to one invention may be made before further action by the
examiner.