There shall be three types of patents possible for filing, invention patents, import patents, and improvement patents. Invention patents shall primarily cover inventions which, on the date of filing or of priority of the related application, have not yet been patented. Import patents shall cover inventions for which, on the date of filing or of priority of the related application, the holder had already obtained an invention patent in a foreign country. Improvement patents shall be those which concern any improvement of an already patented invention.